Go look, I see dell 2ghz machines for 50$ all the time, 3ghz, okay some go for 100$-200$ plus shipping now, but I did just get a 3ghz pc, 512megs of ram, 80 gig hard drive, built in sound, video and network for 50$ plus shipping, I can show you the invoice if you like, I was the only bidder, maybe it was a lucky bid but I see these deals all the time.
Do the math... 3ghz aros pc - 50$ plus shipping
Morph os machine - 500$ plus shipping
Amiga os machine - 800$ plus shipping
While the cost of a AROS capable maschine is indeed very low, your cited cost for a MorphOS maschine is a bit exaggerated. You can run it on any Mac mini G4. Not too sure how much a good deal precisely is, but I heard of many ppl getting a Mac mini quite below 200 US$. For getting a taste of MorphOS you don't need to register, so for less than 200 US$ you will get a system to play around with. If you like it you surely have to add the 150 EUR for the registration (which i US$ is unfortunately a lot especially since the US$ seems to lower its worth even more...).
But if you don't like it dump it off to ebay again, the whole experiment will have costed you some eby fee and teh risk to get a lower sale price than you initially paid for. But prbably your expenses will not exceed 50US$ for testing it.
Anyway trying AROS is for free (give you have a pc around).
I won't even get into a debate on an efika board, Come on a 400mhz processor? I have thrown faster computers in the trash, why would I buy that?
The Efika is definitely not a power house, but a nice little toy which runs surprisingly good. It is best suited for some geeky rojects, furthermore I don't know how much the kWh is charged from your electricity provider, but @ ~0.20 EUR/kWh it saves quite some money to power the Efika on instead of a more powerful maschine (the Efika consumes less energy than my Eee and is fun to use - a thing which is not too true for my Eee). So the Efika is definitely not everyone's cup of tea, but it is not always bunt stupid to use.