Hmm.. That is not my experience at hashcows..
A couple of days ago I had 7MH/s pointed at them for little over 24hrs. Payout so far : 0.035 btc, which makes a nice fat 0.005 per MH/s
I'd prove it to you, but unfortunately hashcows' reporting is the cat's ass (which is the opposite end of the cat's whiskers)..
Here's how I visualize hashcows' inner working : it is a drain circled by some nonsense stats and when you throw in some hashes, a couple of days later some unexplained btc dust shows up in your wallet, with no way to relate it to whatever it is you threw in there. Just like a black hole, information goes in but none comes out
Glad some people apparently got 0.012+ per Mh/s though, good for you.