I went into my local HMV the other day - Bolton - to find that they had two lots of stock of Giotech triggers. There were some which were £2.99 - presumably the new box design - and some which were £1.99, which were a different design. That's the cheapest I've seen them so far.
Granted, there's probably a phenomenal profit being made on these triggers which are basically tiny pieces of plastic, but they're great. They clip onto the R2 and L2 buttons of the PS3 controller- no disassembly required - and make the buttons like they were on the Dualshock 2 controller, not the soft buttons you get by default.