It's tough figuring out a price on 78 albums. Some antique/flea market dealers see them as useless and may sell them by the box -fulls for $25.
I picked up a pristine complete original Porgy and Bess album with playbill-style insert this past weekend for $15. My rule of thumb is to pay a $25 max for an album (generally 4 records) in good condition. Generally I pay less than $5.
I play 78s on a Garrard 4HF with original tonearm. It has speed control, which comes in handy.