Launching satellites takes billions of dollars, and takes years from conception to final testing.
In each case, you can be sure that accountants have run spreadsheets and compared different ways of operation (DBS vs Ka, leasing vs owning, two arcs vs one, old unused satellite vs new one, changing customer dishes vs changing satellites,etc.).
You are suggesting that the accountants either don't or can't make mistakes that can cost Echostar large sums of money. Regardless of my being confused before about the current designated purposes of AMC-15 and AMC-16, everything I have read so far states that Echostar leased those from SES for the purpose of expanding bandwidth on Dish Network. The fact that they decided to use the AMC satellites for something else entirely strongly suggests that the accountants and/or other people in power at Echostar involved in approving the leases for those satellites decided they weren't such a great idea to them after all. It looks like they're trying to make some of their money back on the investment, but at this point they may wish they hadn't leased those satellites in the first place.
Just a thought.