It will depend what the market will bare in your area and how big the breeder is, i sell any color baby here for 25 but others in my area charge by the color, like 35 for whites and 40 for pieds, i also sell 1 year old trios for 150 and in that trio there is a white, a pied and an IB split white.
I have seen 1 year old pair IB's advertised for 250 so to me it just depends on the breeder and like i said what folks are willing to pay.
My birds are totally free ranged so i do not have a bunch of pens to build and my food cost is low so i am able to keep the cost off a birds down.
Check your local adds and Craig's list and see what they are asking and go from there, shop around and be very careful who you buy from, if you go to purchase a bird and see any sick birds turn around and walk away, a sick bird should never be left with a flock and these sinus infections you see talked about on here can be contagious, not always but surely not worth the risk IMO