The SAM board costs about £400 depending on the version and speed. The rest of the £620 is the OS4 license (about £100) and for the rest of the system's hardware: case, drives etc.
Yes, pricey compared to commodity x86 hardware produced in 10,000 batches. However, ask a retailer how much money he makes selling an x86 mobo and then how many he would have to sell to stay in business.
ACube have priced the Sam to make a small profit for the few remaining resellers as well as for themselves and to start recovering R&D costs and hopefully planning for the next stage.
Bit of a catch-22 situation - if people don't buy the current offering, it will be difficult to develop the next one.
And has been said many times, x86 is not possible: (a) there is no license until legal battles are finally sorted and (b) porting to x86 would cost money that would probably not be recouped in sales. Porting to Mac would be great for some consumers, but wouldn't help the wider eco-system, ie hardware developers and Amiga-loyal retailers.
A £600 "hobby" purchase that will last 3 years equates to less than £4 per week - that's less than 2 pints of beer per week over here in the UK. Granted, for many that won't be worthwhile. Unfortunately, that's economics.