Thanks for the reply, I am definitely missing something. I put in equal bitcoin into S7 and S9 hashes. I was able to get 2.3 times as many S7 hashes. Even with the higher maintenence fees I am getting 2x the bitcoins from the S7.

From using the numbers on the calculator, it looks like in 2 months they should give equal bitcoins. After 3 months the S9 should be ahead, but for now S7 seems to work out.