Probably the easiest way to find out current prices of audio gear is through HiFiShark sold or expired. It trawls through a large number of online resources such as eBay, Kijiji, CAM, AAM, etc.
The problem with asking about value is it is very relative. What has value to one person has no value to someone else.
That being said, these cartridges, again, depend on the arm they are attached to. I find Stanton 681EEE to be very bright on some tables and perfect on others. It depends upon the compliance of the cartridge and the mass of the tonearm and headshell. I'm not that fussy on Ortofon OM cartridges. Personally, I never buy a table for the cartridge. In fact, although the cartridge may cause me to buy a table that I would have passed on otherwise, it is still very hit or miss and you can expect to have to replace the stylus.