It seems to be the going rate around here unfortunately. Maidenhead Aquatics is selling them £50 a pair, while my indie LFS is selling them £26.50 each.
My real concern is whether or not they would fight. I'd like two, but not if they might kill each other. I don't seem able to get any definitive answer on that online.
Getting just the one seems to be an increasingly attractive option if one will be happy on its own. £26.50 isn't so bad, I was more concerned about the effect it would have on the price of a pair.