Currently I've just started my second jeep rebuild with my first one not yet completed.
I bought the latest one for $200. It's a 1979 CJ7 that was 90% burned and then left in a field for 5 or so years. My plan is to build a dream CJ7 for $2500 - $3000 including the purchase price and it will have GM 350, Turbo 350, D20, 9"/Dana 44 hybrid front, 9"/Corp 14 hybrid rear, Shackle reversal, SOA, Highsteer, full cage, custom bumpers, 35 mt's, and so on...
But here's the big catch. Over the years I have spent more money in fabrication equipment than most people put into two separate 4x4 projects. I can build a shaved 9"/Dana 44 hybrid for less than $400. I have been collecting parts that myself or my friends were going to throw away and storing them for this occation alone.
Sooner or later you pay for a buildup. In my case I paid long before I ever bought the jeep. You have to be connected and plan on looking high and low for parts handouts and cheap used items. Without all of them you'll spend more than if you bought someone's that is already finished.