It depends on the overall condition and the specification.
If it's the 1.67Ghz model, casing is in excellent condition, the logic board work fine, as does the supper drive, then your looking at 80-100. If the casing is not in very good condition and it has other faults other than the display, then your looking at 40-70 max.
I hope this helps.
P.s These are only estimates based on my own experience of buying broken PowerBooks for spares on eBay.