Yeah you're right, that's obviously not going to be exactly the same a double-sized field. Though there is kind of the suggestion in the poker client that the 1st place prize will remain at least $100k.
Quote:
The Sunday Million is the world's biggest weekly online poker tournament, with a first placed prize regularly over $100,000
Bolding theirs. I guess that's no guarantee it will remain over $100k but it would be strange wording to add if they weren't planning that (found that in the 'news' tab of the client). Not quite the $150k now, but would a 6-fig 1st place be prestigious enough?