Unfortunately, those 45 series tires are not your average 40K mile tires. Because of the different rubber compound used to stabalize the low profile they wear considerably faster. They may look ok, but at 5K you've probably used up 20% of their life. In general, used tires are not worth much, but a local tire dealer may take them off your hands. Otherwise you can usually advertise them in a local autoparts or grocery store for free. As for value, you can check the price of new ones and figure getting about 50%.
Hmm... I suspect a fair price would be less than the cost of four new aftermarket wheels. True some may value the Volvo OEM wheel more than an aftermarket set, but you would need to seek out that type of buyer. Have you tried calling junkyards and seeing what they would charge for a set of Tethys wheels?
If you decide to sell, can you please let me know what your asking price is?