The money is by far the biggest incentive to go. Do UO and WA really want to try and compete in that conference with fewer resources than Rutgers, Indiana and Illinois? They would never sniff the playoffs.
Conversely, if they jump to Big 12, they still make great money and have a much more reasonable path to the playoff while being on equal footing with their primary competition.
Call me crazy but I think any team joining the SEC or B1G without a full share is giving their football program a life sentence of mediocrity at best and conference doormat at worst.