The rewards don't seem worth it. Rather give bigger rewards for completing categories or a unique decoration. For completing all economy achievements perhaps a watermill or silo or improved silo? For completing all social achievements perhaps a decoration that can only be gotten through achievement system. A statue of 2 golden settlers shaking hands for example? It just needs a few unique things that can only be found through the achievement system. 200 gems here 200 coins there. Not really. I'll still probably try and get them all even with the bad rewards though :P