Indeed, an FPGAArcade at around £200 + case + PSU is well worth it for what it provides.
A Natami, if the 68050 performs as well as it is hoped to perform, will also be worth it for people that need higher performance out of their Amiga. A smaller market for sure, but the more powerful FPGA will cost more, and then there's the second FPGA on board as well.
Btw, case makers - make sure you leave space for a 2.5" hard drive in the Natami case designs!