The way I see it: the all up cost for an Xtracycle conversion really depends on what you're starting with. I started with an early 90s Kona Lava Dome, rigid fork, pretty much perfect in terms of compatibility (rear dropouts 7mm thick, rear hub spacing 135mm, etc... the Free Radical fit perfect).

However, the old bike had cantilever brakes. So I had to upgrade to v-brakes (the Free Rad only works with v-brakes or disc brakes, and if you're doing the rear you might as well do the front too). The original rims & hubs were shot.... New wheelset, with a dynamo front hub for the new Lumotec lights... you can see where this is going, I suspect: Depending on your needs/wants/desires, you may not really end up saving much (or any) money converting an old bike on hand, even if it fits the X kit perfectly. You might find it's just much better off to spend a little more coin up front and go with the Big Dummy... don't know, just sayin'

Would I do it again? Yes! I've gotten more use out of the Kona as an Xtracycle than I ever got out of it as a mountain bike. It's setup just the way I want, and it gets used every weekend to haul our kids down to the beach or wherever we're going. Do I wish I had a Big Dummy? No, because at the end my X conversion still came out a little cheaper than going that route, and for what I need/want it for, it works just fine. But by the time I was done, I did sorta question the whole financial logic of it all...

Steve