One can buy right now a MISTerFPGA from aliexpress for around €150 and that can emulate both MVS and AES. On this side of the pond, a VGA to SCART cable is all that's required to connect it to a CRT TV.

If instead one want the real HW, a working MVS PCB can be found for less that €100. A JAMMA cabinet would be the perfect place to use it, but with a supergun a CRT TV can give the same results. Cheap superguns can be found or built for around €30, fancy models can cost between €200 to €300 tho.

The carts aren't cheap tho, specially if original. I've only a battered "Puzzle Bobble" cart, it's a really fun game in PvP, but probably not the more iconic NeoGeo title.

Puzzle Bobble, actually, is definitely one of the more iconic Neo Geo title. If you open it, you may have a surprise. The game was such a success that Snk itself had to butcher other, less successful games (essentially Power Spikes II if I remember correctly), to produce conversions/bootlegs and answer to customer's demand. It has one of the best replayability of the system, it's very fun playing versus, plus, girls absolutely love it. There have been many sequels, but none live up to the original despite the additions, and they’re all more or less unnecessary.

This is what I do. There is also an overclocked core that drastically reduces slowdown on Metal Slug games.