I got my Blade/San Francisco for £75. From time to time there are deals, Argos was selling them on discount, some online retailers were too, Orange had a weekend sale on them a few months ago, and of course the second hand market. But yes you are right, they are closer to £100 than £50.

http://blade.modaco.com/ is a real gem and truly the best place to get all sorts of roms for the phone.