I'm quite happy with my SAM 440, but I am also not delusional enough to think that in sane terms I got the best bang for my buck with it. I could have built 2 fairly nice midrange gaming pc's for what I have sunk into the SAM rig.
At the time, it was the most powerful "Amiga" available for purchase from a retailer, and I like OS 4. That being said, it doesn't even remotely come close to doing what I expect a modern PC to do as far as being a computer I'd solely use for every day to day tasks. High costs on these modern gen "Amiga's" will always be an issue, and the availability of cheap macs and MorphOS is often a more viable option than the OS4 rigs, sadly. Same goes for AROS and old commodity PC HW. Just not enough manufacturer volume to make the new PPC OS4 rigs affordable to most people.
Performance vs. cost on this stuff is sort of redundant as a comparison, no one is buying them for a daily driver unless your needs are far less demanding than most peoples. I enjoy my SAM for a vague nostalgia factor, enjoy the lack of noise it emits, but in all truth my iphone does more than the SAM does in the "modern computing" aspect for me. I love the SAM, but I'm fully aware of its' limitations, I suppose. No one twisted my arm to buy it at the steep price that I paid for it.