If your budget for buying a new automobile is in the neighborhood of $20,000 or $30,000, or maybe even $40,000, there are loads of cool cars to choose from. A nice variety of crossover SUVs, mid-size sedans, and the lower end of the sports car market can be found here as well.

But, for a car enthusiast, there are some much more appealing offerings on the used car market for that same price range. One particular type of car that stands out here is the luxury sedans. It's no secret that 10, 15 or even 20-year-old luxury sedans have been obliterated by depreciation, so the prospect of owning one seems tempting. But there are several different reasons why it's a bad idea.

8 Reliability Concerns

2005 BMW 7 Series E65 - front quarter
Via: BMW

This is undeniably the biggest and most solid reason as to why buying a used luxury sedan is a bad idea; the reliability concerns. Luxury sedans from the 2000s are filled with all sorts of complicated pieces of equipment like air suspension, night vision cameras and other such accoutrements.

The rear of the E65 7 Series
BMW

RELATED: These Are The 10 Most Unreliable Cars Ever Made

They also have massive, hideously complicated and hopelessly unreliable engines. As a result of all this, most older luxury sedans are famous for being a total reliability disaster. The E65 BMW 7 Series (pictured) is a particular example, as it's widely regarded to be the absolute worst generation of the 7 Series, thanks in no small part to its reliability, or lack thereof.

7 Outdated Tech

The interior of the D3 Audi A8 W12
netcarshow.com

Back when all the luxury sedans in this price range were launched, they featured all sorts of exciting new tech that no other car at the time had, not even on the options list. The infotainment screen in the D3 Audi A8 slid out from a hidden compartment in the dashboard.

The interior of the W221 S-Class
netcarshow.com

Meanwhile, the W221 Mercedes-Benz S-Class was one of the first production cars to be fitted with what we now call auto emergency braking, along with a raft of other extremely high tech components. At the time, this stuff was state of the art, but nowadays and by modern standards, it's totally outdated, and gadgets in modern cars have way surpassed it. Most of the nav systems in these cars rely on DVDs, the graphics are blocky, and the systems themselves aren't all that nice to use. In some cases (BMW's first generation iDrive), they can also completely give up.

6 The Immense Maintenance Costs

The front of the facelifted VW Phaeton
Volkswagen

Luxury sedans have pretty much always been very complicated vehicles. The budgets for making them is much larger than the automaker's other models, and there's a lot of leeway to install a lot of complicated components. The problem is, all of these components are very expensive.

Black VW Phaeton parked
Volkswagen

RELATED: Cool European Cars You Can Buy Dirt Cheap... But Maintenance Costs A Fortune

The annual service costs for a lot of these older luxury sedans can add up to thousands of dollars, and a component that may cost a few bucks off Amazon on a cheaper, commuter car, the luxury sedan will demand several hundred dollars for the same part, plus even more to get a mechanic to install it for you. This is another major contributing factor in the depreciation of older luxury sedans.

5 They Will Continue To Depreciate

The Maserati Ghibli in blue
netcarshow.com

A brand new Maserati Ghibli, which was recently electrified, starts at well over $70,000 for the base model. That's a pretty steep price, but a used Ghibli can be found for less than $30,000, even with relatively low miles. That might sound tempting, but, just remember that it's a Maserati, and that it's also not a very good car. Once you buy it and start putting miles on it, it can only depreciate even more.

W221 Mercedes S65 AMG in silver
Via: Mercedes-Benz

It's the same story with older Mercedes S-Class models. This $90,000 luxury sedan can now be found for around $30,000 as well, and in some cases, even less than that. Again, that might seem tempting to you, but as a wise man once said, nothing is more expensive than a cheap Mercedes-Benz, which will only continue to depreciate further as well.

4 A Lot Of Them Are Neglected

The front of the 2008 Jaguar XJ
netcarshow.com

Have you ever been somewhere, and you see a random older Mercedes S-Class that looks like it's completely sagged with its wheels tucked under the arches? That wasn't the owner's choice; there's a very high chance that that particular car suffered air suspension failure.

The D3 Audi A8 4.2 TDI in gold
netcarshow.com

The truth is, a lot of the owners of these cars simply aren't ready for the maintenance costs and the potential ticking time bombs that they all have, and some of them are unfortunately unable to pay the price for a new part or a service. The upshot of it is that the cheapest used luxury sedans on the current market have very probably been neglected by their owners.

3 Terrible Gas Mileage

The 2008 Audi A8 in black
netcarshow.com

Luxury cars from the 2000s came in a variety of engine flavors, but they all had one thing in common; they were all massive, powerful and hideously complicated to repair. During the 2000s, the main three German luxury sedans were all offered with 12-cylinder engines, with the Audi A8 adopting the infamous VW Group W12.

The Maybach 62 S in black and blue
netcarshow.com

The Maybach 57 and 62 also had the notoriously unreliable Mercedes Benz V12, and depending on where you are in the world, there's a chance that VW sold a Phaeton with a V10 diesel engine in your market. While all these engines are powerful and sound cool on paper, all of them get terrible gas mileage, adding more and more dollars to your, probably at this point already, massive repair and maintenance bill.

2 You'll Get Some Looks

The Maybach 57 S Special in black
netcarshow.com

There's one positive side to a lot of older luxury sedans; a lot of them are very subdued, and they slip under the radar quite well. While some people may think you're rich and will have no idea that you just spent $15,000 on a Bentley-engined Volkswagen sedan, there are some other prejudices that you will be blessed with while owning a used luxury sedan.

The rear of a black VW Phaeton V8
netcarshow.com

RELATED: These Understated Luxury Cars Are Perfect For Flying Under The Radar

There is a risk that you might get looks from people who think that you're that type of person that drives a luxury sedan. You know the one. Car enthusiasts, meanwhile, will give you a different look; while most of them will appreciate and admire your new purchase, if they have any knowledge of the sedan that you chose, they might just presume that you're on your way to the mechanic when they see you on the street.

1 Insurance Costs

The front of the E65 BMW 750Li
BMW

Finally, there's the last relatively big issue with buying a used luxury sedan; the insurance. The insurance rate can depend on a lot of factors, but the truth of the matter is that it's very expensive to insure a used luxury sedan.

The rear of the E65 BMW 750Li
netcarshow.com

Depending on your age, state where you live, credit score and various other things, you might be able to get good deals on insurance for your cheap luxury sedan, but just be aware that they will exceed just about any insurance rate for a brand new "commuter" car that costs the same amount of money.

NEXT: 10 Affordable Luxury Cars You Never Knew Were Super Fast