The first two are Testudo gracea subspecies. The second two are Forest Hingebacks, Kinixys erosa. Two very different species of tortoise with very different environmental requirements.
In terms of "market value"-Russians are everywhere and can be found fairly inexpensive. Most "Greeks" regardless of subspecies are around $100-200 each, depending upon subspecies and size. Forest Hingebacks can vary greatly in price. There are many advertised on Kingsnake.com right now. The prices vary from $35 all the way up to $400 each depending upon size & gender.
Thanks GB......I was hoping you'd respond with regard to the Greeks . I thought the hinges were erica too but was not 100%
I understand their diff care needs but am worried because the lady offering to trade is keeping all 4 together right now in a 40L. She admits she does not know what to do with them and has only had them for a week.