Actually, it is not available through the Trophy-Only option. That is an opt-out of wagering and what I proposed was an opt-in. Totally different psychology between the two.
While talking about psychology, I think something important is that a player feels more "emotionally invested" in an event for which he/she has suffered a little pain (in the checkbook). By paying a larger amount event....the more it feels like a big event - differentiated from a weekly league sort of event. The recurring whining about cost is almost a necessary by-product of the necessary pain.