Are you sure you're not confusing the propositions
o=ASK => a=PAY
and
a=PAY
?
If not, could you present your argument formally?
I thought your post asked about the proposition "o=ASK => a=PAY", and didn't mention the other one at all. You asked this:
Omega asks you to pay him $100. Do you pay?
not this:
Do you precommit to pay?
So I just don't use the naked proposition "a=PAY" anywhere. In fact I don't even understand how to define its truth value for all agents, because it may so happen that the agent gets $1000 and walks away without being asked anything.
This problem is roughly isomorphic to the branch of Transparent Newcomb (version 1, version 2) where box B is empty, but it's simpler.
Here's a diagram: