what are you starting with? a 6 cyl. car or a small block car? if your starting with a 6cly. car then i'm telling you its damn close in price because the big block and small block swap need to basically have the same things done.
as far as the price of the motor goes, what ya use will make a big difference in price also. on th big block side a 440 gets top dollar in this area. a 383 or 400 an be had cheaper then the 440. with small blocks a 340 will fetch top dollar and a 318 or 360 can usually be bought alot cheaper.