Pre BAD SLOs I'd guess in the 3500-4K range. 70s Marshall cabs? Lots of variances, so we need to know what year...condition....73 or earlier would have Pulsonic GBs, 74/5 would have RIC or first version blackbacks. A mint 73 or earlier can fetch 2500-3K if original, no wonky speaker issues(cone rub/cry). For example, I picked up a MINT 77 slant w/T1511s last year for 1500.
These prices are what I'd consider reasonable and a good value for both. Some sellers of these think they have gold bullion and ask WAAY too much...but, I digress.
Find out those specifics and you'll ge a better estimate on the cab. Look for date codes on the speaker frame, and cone codes on the cones themselves( you'll have to look under the frame closer to the magnet to see).
If the speakers have any re cones, those are basically worth the same as a modern speaker. No vintage value at all.
