e-bay is creating value tokens (money) that are similar to gift vouchers.

I checked with Which? They say;

What are my gift card or voucher rights?

The company that's issued the voucher should include any important terms at the point of purchase.

Always check the terms written on the voucher (or the packaging around it).

If the terms were not prominently brought to your attention when you purchased the gift voucher - for example, they were hidden on the reverse side of the card or voucher and this couldn’t have been seen because the card was stuck down or enclosed in packaging - then you may be able to argue that the terms are contrary to the requirements of good faith.

To meet the requirements of good faith, the terms must be designed, negotiated and entered into with you in a fair and open way.