Pricing for Groups of Cards

[scottpt99]

How you you go about setting a price cards when buying them?
I know you have to take into account condition and all.

I have the opportunity to purchase some cards from 1970, 1971, and 1972.
After looking through them some general thoughts.
1970-Several have writing or name on the back a few on the front, many have worn corners, mostly common, but some from higher series
1971- Better condition but still not stars, includes higher series
1972- Most in very good condition and some stars included and higher series

Do I price each card and give a certain percentage of book value based on condition (10% poor, ?? others??)?

Not wanting to make a bad deal either way. I know you won't be able to give a price without seeing or knowing the cards, but I am interested in you thoughts on how to price it.

Thanks.