Will be based on rack space requirements, I am going down today to get exact measurements and figure out the typical BFL and avalon space requirements. 1 rack space costs 53 eu with all power costs included, and 2 rack space costs 85 eu.

The question will be how much can we fit depending on your setup in one rack or two, the key being no extra costs for heavy power usage, which if you fill lots of avalon or BFLs in the rack space could be very very cheap in the scheme of things.