I don't think the thought experiment hinges on any of this. Suppose you were on you own and Omega offered you certainty of 80 years versus 1/10 of 800 and 9/10 of nothing. I'm pretty sure most folks would play safe.
The addition of people makes it clear if (grant the rest) a society of future people would want to agree that those who 'live first' should refrain from life extension and let the others 'have their go'.
Loss aversion is another thing altogether, if most people choose 80 sure years instead of 800 years at a 1/10 risk it doesn't necessarily prove that it is actually less valuable.
Suppose Omega offers to copy you and let you live out 10 lives simultaneously (or one after another, restoring from the same checkpoint each time) on the condition that each instance dies and is irrecoverably deleted after 80 years. Is that worth more than spending 800 years alive all in one go?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.