Assuming no additional revenue, each Pac-10 team would see something like a 17.7% decrease in revenue with the addition of two teams. It may seem nit-picky, but when we're talking about millions of dollars that matters.

But revenue was never going to be stagnant. Expansion allowed for more leverage when negotiating TV deals. Expansion also allowed the Pac-12 to hold a conference championship game without having to beg for an exception (like the Big XII).

Utah and Colorado joined in 2011, and P12N launched in August of 2012. It's absolutely certain that the promise of an expanded conference with additional markets added negotiating leverage and allowed the conference to command a higher price. I wasn't privy to the negotiations, but my guess is (since CFB seems to be a pretty selfish business) that adding Utah and Colorado brought enough value to outweigh the 17.7% hit that the conference would have otherwise taken.

Finally, it's worth noting that Utah wasn't an equal revenue partner for several years. So there was a significant period where Utah contributed millions in value to the conference (as a leveraged "market" for the network negotiations) without drawing a full 1/12 of the revenue.