My 89 190E Evolution 2 set me back 2 months worth of food and entertainment back in 2004. Total went up to 46k and considering the size and features from the 190E E2 (amg/track etc) vs 750 top of the line 02 goodness, I would say the E32 is prolly gonna hit 60 ish K if it's been left to rust. The E2 would've cost 30 ish if parts could be found locally instead of sourcing on MB and their european 50? (random guess but they have to reproduce parts upon request for cars for a specific amount of years) year production law.
A classic restoration project, at most times should be about the joy of restoration. It's not cost effective most of the time but the feeling of driving a brand new classic 10,20,30 years down the line is one of the best experience out there.
My next project will definitely be an 8 series but based on the above statement, no cash no go.