Chris, as for your statement about some of the teams not wanting to make the trip, "the cost of travel and potential winnings don't make sense," I have to disagree. I just looked at the payout for Pro Mod at the US Nationals. Winner gets $10k, R/U gets $3k. And that's the same payout for all of the Pro Mod national events. No money to semi finalists, only the winner and runner up. Now of course, that doesn't count contingency money the winner and runner up could also collect so I'm not forgetting about that, but at Indy you have to qualify against 25+ other cars, make the field of 16, then win the event to get $10k. At the World Series, there is no qualifying as everyone makes the field, you race one additional round of eliminations, and the purse is 10x the amount of a regular national event!
Another way to look at it:
Indy = 25-30 cars show up, 2 cars collect $13k plus contingency
WSOPM = 25-32 cars show up, 1 car collects $100k
I guess in my mind, if I was running a top tier/middle tier Pro Mod team, I would figure out how to get the costs of the WSOPM into my yearly budget as the reward is well worth it.