I built an 8-lamp 40-watt high output exposure unit for about $350.
Depending on the size you want to print, you could certainly make it
smaller or larger, depending on your needs. You can also save money
by using standard ballasts rather than H.O. and lower wattage bulbs,
but I felt it was worth the extra $$ to have the shortest print times
that I could. I built mine based on the plans in the Palladio
Company info packet. Call them at 1-800-628-9618 and they will send
you a copy. It also contains some good information on making enlarged
negatives as well as a price list for their wonderful machine-coated
Pt/Pd paper and supplies. They are good people!
Kerik