I think the only people who would be surprised at the $20K figure would be those who havent had their bronco long, or hadnt really taken it apart to make it somewhat new again. If you do any regearing and upgrading of the axle shafts, locker (air, mechanical, etc), joints, bearings, brakes, seals...your looking at $2500-3000+ and thats if you've shopped around and had "deals" on some of the gear installs...if no deals the price goes up, up and away...and thats just axles. Fresh motor (all about how far you want to go), fuel lines, fresh radiator, engine accessories, induction upgrades...figure $3000-6000+++...and it goes from there. Stock is great, but with the price of gas, efficiency is key...regearing, upgrading the tranny, fuel injection...it adds up quickly...top that off with rust repair, body work, quality paint (not show paint, but quality paint)...its not cheap even if your doing it yourself. $20K would be a minimum needed; 30K or more is more realistic...and thats doing the majority of the work yourself.
I have a bronco buddy here in town, he bought a pretty nice truck, got a couple of deals on some addional parts (tires, wheels, soft top), has gone back through and fixed some wiring (not rewired), stock-swapped some suspension parts, other "maintenance"-type work, etc; nothing "hard-core" or too invasive mostly stock fixes, maintenance and replacing worn out stock parts and he has spent probably close to $5k (on top of what he paid for it) and hasnt even thought about body-work, repair, etc...no major engine work, etc...it runs great and he is having a good time and using it as a DD most of the time....which is what its all about. My point is, it adds up quickly...very quickly.
Salgood, its looking good; keep us updated.