For the SSK, somewhere in the range of 150 GBP on the high end, and no end on the lower side. I won't give you a direct price (that's up to you, possibly with some help from a purchaser), but 220 GBP is too high, and 150 GBP might be as well.
For the ErgoDox, maybe somewhere in the range of 90-150 GBP. Depends on various aspects of it: fullhand or not, aluminum or not, etc.