I bought mine used (or rather mounted; never run) for about $100; also the water/meth injection kit I got for about $150 so my build will be quite inexpensive, but then I have a lot of money into the ECU and EFI stuff already. Plus I fabricate most of the HW myself
If you start out with a carbed engine with a distributor, you are looking at a significant cost.
I paid 160 for my amr and got lucky and found the turbo Saab vacuum can for 18 on ebay. Then roughly 15 bucks worth of hardware. Stock d/p intake, 034 dizzy, I already had a w/b o2. Ran a single kad but couldn't get it to run lean enough on cruise so ended up with a 60's Rochester from a straight 6, drilled the jet one size and the afr's were as perfect as you can expect for a carb I was really surprised.