An 8-team playoff would definitely generate more money than the 4-team playoff but I do think there is a strong possibility that the overall amount of money generated by the sport as a whole might decrease because all of those OOC games would become exhibitions and nothing more. As it stands now, Ohio State's game against Cincinnati was hugely important because a loss there *COULD* have kept Ohio State out of the CFP. As it turned out this year it wouldn't have, but it *COULD* have. Thus, the tOSU/Cincy game was hugely important to tOSU fans. If the B1G Champion got an auto-bid then an early season game between tOSU and Bama wouldn't really matter much other than for seeding so who cares?
But there's a flip side.
Let's say we're looking at 2015 OSU. That team didn't attend the CCG due to the loss to MSU, their only loss of the year. OOC, they played Virginia Tech, Hawaii, Northern Illinois, and Western Michigan.
Do you think that OOC slate would have been enough to secure an at-large bid? OSU dropped to #8 in the rankings after that loss. What if it had been perceived as a down year in the B1G and they'd survived a couple close calls (they didn't, in this case). If you assume 6 of 8 slots are gone, that leaves two slots. Iowa was perfect in the regular season, but lost in the CCG, and finished above OSU in the final CFP rankings. Notre Dame was 10-2, and finished one slot behind OSU in the final CFP rankings, but they're Notre Dame. Florida State was also 10-2 and two spots behind OSU in the final rankings. I could see the committee giving Iowa a shot and rather than allowing 3 B1G teams in, giving the final at-large to Notre Dame.
Look at 2016 OSU. Again, they missed the CCG due to a single loss against PSU, but made the CFP. The B1G was strong that year, but what happens if you replace the Oklahoma win with Youngstown State? Do they still get the benefit of the doubt for one of two at-large slots without that big win?
Then look at 2017 OSU. As a 2-loss team, they missed the CFP, and one of those losses was a premier OOC game against Oklahoma. In the 8-team system, they would still make the playoff as they won their conference, so scheduling a team like Oklahoma OOC isn't a hindrance.
This year, Clemson's only decent OOC wins were a terrible Georgia Tech team and a mediocre Texas A&M team. Their conference was terrible. If they'd lost a conference game and missed their CCG, I'm not sure those OOC wins would have been enough to secure an at-large slot.
OOC can be important for strength of schedule if you don't win your conference, and an OOC loss can be a mulligan if you do win your conference.
Today it's probably best for premier teams to schedule OOC games against weak-to-middling P5 opponents. Teams good enough that they don't look terrible for strength of schedule, but teams who you are reasonably expected to easily beat. Because as
@OrangeAfroMan points out, we often rank teams based on number of losses, not quality of wins. It's better for OSU to beat Boston College out of conference than lose to Oklahoma out of conference. But if you make conference championships an automatic qualifier, a team like OSU that schedules OOC against Oklahoma can still lose that game and make the playoff by winning the conference, and winning that game [but missing the CCG] gives them a better shot at the at-large bid. It actually makes it easier to justify scheduling harder OOC.
