No, I don't think it is right, as the NHS is struggling with funds as it is, and to make money from a free prescription issued in good faith by the doctor is morally wrong.
Many diabetics can't get a prescription for test strips at all, so why should some greedy person gain from using the NHS's money and our taxes?
As far as I'm concerned e-bay shouldn't be allowing this, although to be fair, it is almost impossible to police the sellers as some could be genuine in that for example, they have strips they bought for a glucose meter that they no longer use, and wish to sell them on.
It's all about your personal conscience I suppose, but many sellers don't sell the strips any cheaper than you can get them direst from Abbot for example. Buyer beware!