My FaceTube feed has been full of Army buddies' pics of their brand new ultra-expensive ARs and AKs. I am incredibly suspicious of new manufacturers, especially when their prices are three or four times what a service rifle costs. While I'm not going to name names, one guy in particular paid $2400 for an 18" direct-impingement AR with a fancy paint scheme. For that money, you could spec up your own build and have the mother of all ARs. Or for half of that, you could build a top-shelf service rifle.
I guess I'm writing this as a word of warning. Just because you pay three times the market rate for a rifle doesn't mean you're getting "the best". In fact, if you're hell-bent on spending your life savings, you're a lot better off to go to a reputable smith and have him spec up a rifle for you. Or build a nice service rifle and then get an awesome scope like an ACOG or the US Optics 1.5-6x I've had my eye on for a while.
There are reasons to pay more for a rifle. For instance, BCM's M16 bolt is all machined steel and has a heavy duty coating. It costs twice as much as a "semi auto" bolt with a MIM or cast extractor and gas key. But it is far more durable and because of its greater weight, will help slow the cyclic rate and be more reliable.
Additionally, the Vltor A5 actually slows your cyclic rate and will make your pistol or carbine more reliable and nicer to shoot. If you're stuck on a rifle (like me) the Magpul rifle stock has more storage space, is more comfortable, and is easier to bag down than an A2 stock. They cost more money than their alternatives, but they're worth it.
In short, do some research and make sure you're paying for actual parts and not blue-sky and a fancy paint job. Nice ARs do cost a little more, but you should be getting real, quantifiable performance upgrades for the increased cost.
AKs are another story entirely. To oversimplify, an AK is an AK. Romanian WASRs are of notably terribly quality, with a well-known canted sight problem (among others). They used to be FAR cheaper than the other makes, but now they're all about the same $500, so buy a Yugo or a VZ58. You can spend $1000 on a very pretty Arsenal AK, and I have a hunting buddy who did just that, but his Arsenal is no more accurate, nor any nicer to shoot than any mid-price AK. All that money paid for is a milled receiver, which is very pretty to admire for its flawless machine work. But the tolerances are about the same as any of the cheaper stamped models.
Do your research and don't get suckered by pretty finishes. Build the rifle you want, and putting a pretty finish on will only run you another $200-350 in cerakote. Caveat emptor.