Better to have and not need, than need and not have.
The price of entry into the AR/AK market is substantially cheaper today than it will be in the future, so set aside what you can reasonably budget for without selling a kidney and pick something up as soon as it crosses your path. It’s irrelevant what things cost previously, because you weren’t licensed then. Coca-Cola use to cost a nickel back in the 1950s (I think) and now you pay $2.00 for a soda... but you don’t complain about the inflation of that, right?
If you can get a pre-94 Colt AR lower or other reputable brand, you can build it out with almost any feature you want (no grenade launchers, unfortunately...) They exist, but you’ll pay close to the market value of a lower end AR. You can then marry that lower with what ever Gucci high end parts you want. Buy quality parts that are well known for reliability and your gear will last. Some brands might include BCM, Daniel Defense, Noveske, Knights Armament, just to name-drop a few.
If you don’t want to go the AR route, there are alternatives that still utilize standard capacity USGI pre-ban 30 round magazines, such as the Scar 16 or Sig MCX, as well as bull pup varieties made by Tavor and Keltec to name some other alternatives. All have pros and cons, and mostly it’s a matter of preference.
There is literally so much information out there these days, you can lock yourself in your house for a week and binge watch YouTube and you’ll never get through it all...
For my money I’d buy an AR because it’s America’s rifle. Alternately, an AK pattern rifle had been used in every conflict around the world and is proven to operate in the most extreme environments. Alternates mentioned are currently not prohibited because they fail some of the similarity tests imposed, but that also impacts price and availability.
My opinion is you’ll easily be in the $3-5K range once all done, assuming $2K+ for a carbine, then optic and ammo. Make sure you get training so you can be proficient, and above all else, for God’s sake, make sure you look good LARPing with it... if you don’t look good, it doesn’t really matter, right?
post a pic when you get it and happy shopping!