Yes, they are worth it. There are a few catches though:
You cannot play them on your home system without a converter.
MVS carts are not censored like their US AES counterparts (IE: you get blood, bounciness and fatalities right out of the box).
You will need a 1, 2, 4 or 6 slot MVS board to play them (preferably inside an arcade cabinet). The number of slots relates to the number of carts the board can hold at any given time. You can switch between the games with the "select" button that can be found on most Neo Geo cabs.
If you don't have the room, you can get a Supergun (or similar converter) that will allow you to play your MVS jamma board with a couple Neo controllers and your TV.
They are cheaper because they were originally geared toward arcade-only use. Arcades have little to no use for the original King of Monsters anymore so you can pick one up for $10. They usually don't have fancy artwork or boxes though, but you can find complete sets for a few more clams.
You can get a complete 29" cabinet with an MVS board already hooked up for around $400. After that it's just a matter of picking up a bunch of $10 - $20 carts and having a blast. If you have the room and are close enough to pick it up yourself ($150 shipping costs are a bitch) then there is no better way to go.