If AM had 20 Ph/s in their mines and the network hash rate was 250 Ph/s (as predicted by genesisblock), then it isn't possible for AM even get 10% of the network. That would require 25 Ph/s. Once their chips are all used up, it's all downhill until new chips arrive.
Clearly, you didn't even bother reading what I said.
I do agree that the days of AM self-mining 10 to 20% of total network hash are likely over. But that doesn't matter.
AM isn't going to sell 20P and then go out of business. That is the FIRST BATCH of their next gen chips, which based on the prelim target specs will be highly competitive both in wafer cost and power efficiency.
It doesn't matter if AM self-mines, sells turnkey miners, or just sells chips as long as they are maximizing their profit. Is the profit margin for selling mining hardware decreasing? Of course, but based on the specs AM will be able to get a very healthy profit from their chips and/or miners.