If you go all out with all the bells and whistles (high end computer, 3 screen setup, 8 contactors for force feedback, LED flashers, shaker motor, decals) you could easily be looking at $3,500. If you cut back you could probably get the cost down to $2,500 with just the cabinet (if you build it yourself or find a donor),
I would say you can go 4k+ for a nice 3 monitor setup all the way down to the $1700 range for a 2 monitor mini-pin.... It really depends on what you put into it. Don't go cheap on the CPU or the Monitors - get what you are gonna keep - they are basically impossible to upgrade later. I got 4k+ in mine. I love it, and it's VERY valuable to me. Honestly, it's not the real thing, and I don't think that it would stay in a larger collection. In a smaller collection of 1 to 4 machines, it's great. You can get the "feel" of playing 100+ HQ games in a smaller collection, and even thought it's not real, it is still awesome pinball fun. Obviously, I am biased, as I have made 5 (yes, I have did some serious upgrading). http://www.youtube.com/boogies2
Here's a link to the Hyperpin forums: http://www.hyperspin-fe.com/forum/forumdisplay.php?32-HyperPin-General-Discussion That is the best site IMO for researching how-to's on a cabinet.
That is the front-end software that launches the visual pinball / pinmame program. You can get tons updates through this site. I use the VPForums for keeping up-to-date with table that are WIP and newly released.
You DEFINATELY need to try a decent setup to decide if it's something that you would enjoy. If you have a High-End Gaming PC, you could probably run one of the tables as a test and see if it looks like something that you would enjoy. I would recommend trying all real pins in the same manner of "try before you buy", but with the Virtual Pinball setup, they are kinda far and few between, but the scene has definately been growing.