Yes, it does boil down to $$$$$$$ for most bowls. One rather glaring manifestation of that circumstance this year is that Texas (7-5) is going to the Holiday Bowl, which is higher in the Big 12 'pecking order' that the Alamo Bowl, in which the B12 rep is Baylor (9-3), which soundly beat Texas last weekend. It comes down to more fans, and thus more business for hotels, restaurants, and Sea World if UT's fans, rather than Baylor's, come to San Diego.
Still, $$$$$$$ is directly related to tradition, and some old tie-ins and in-season rivalries and proprietary (that's selfish) conference ties that influence which tack the bowl situation is sheeted in. The Big Ten especially wants to hold on to its gluttony about its traditional Rose Bowl berth, and seems to think if its champion play in the NC it should still automatically get its next team in the Rose. 2 BCS games are now worth $34 million, plus that trip to southern California for the snowy, windy midwest fans remains a goal that other regions (they think) aren't so entitled.
The argument about a 4 -team playoff, such as this year's LSU, Alabama, OK St., and Stanford, is that in any year there may well a fifth team with as much claim. Same thing for an 8 or 16 team playoff. Well, all other sports do have that same type of dilemma, but the champion which emerges is not in dispute as often was, and still can happen, in football with the BCS [e.g., LSU and USC, 2003]. And it's rubbish that the regular schedule 'won't mean as much' is there were a playoff. Can you imagine there having been less significance to the LSU-Alabama match last Nov. 5 if they knew their teams would surely make the playoff system anyway? That was virtually the case as it was-- and both knew their quest for the NC was out with another loss-- also the same.