To a 'house' that ticket is worth $1.46M.
You hold the ticket. And you could collect bets of $1.46M on Vegas to win.
If Vegas wins, you collect $2.5M but you pay out $1.04M to the people that bought Vegas to win above (net $1.46M)
If Vegas loses, the original ticket gets framed, but you collected $1.46M in losing bets (above).
Either way, you have $1.46M when it's over.
The guy holding the ticket isn't a bookie (presumably), so he can't do that. But a house can. So they offer him $1M. Tidy arbitrage for them.
If I was him, I ask for $1.25M (and take it if offered)
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