Only in bitcoin land would a 30% yield be considered low. And sure, for a miner you need to make your money back rapidly before more miners appear, but AM has shown themselves to be a fairly reliable company so far, with a longer term perspective. In the ordinary investment world 30% is unheard of. Literally, unheard of. That that sort of payout is available from AM shows the amount of risk that is still present in the Bitcoin world, and more importantly, shows how thinly traded it even its most heavily traded issue actually is.

Due to the finite nature of bitcoin rewards (lets not mention transaction fees), there is certainly a cap on AM's value, but I think it could justifiably be a bit higher than 4 BTC /sh if they're able to regain their previous posture with the rollout of their 2nd gen chips.