Amazing Race boosted GSN's prime time ratings noticeably in July and August, when the show was fresh. The demos even got younger, which is, well, amazing for GSN. This network usually skews older than most hills.
The effect wore off, though, which does tend to reinforce the cliche that reality doesn't repeat well. Or, more accurately, multi-episode serials don't repeat well. Most viewers just aren't willing to commit to many hours of watching a series when they know the outcome.
As for the price tag, it will hardly bankrupt the network. Unfortunately Liberty no longer breaks out GSN in their financials, but the network was taking in about $90 million a year at last report. Amazing Race was a major commitment, but amortizing the price tag over the four years of the deal makes it bearable for the network, even if the show is no longer a ratings winner for them.
My guess is that Amazing Race will be back on a more regular basis some time in the future. No question the new prime time schedule after Millionaire is something of a patchwork, with the cash-game poker series getting a lot of exposure. I kinda like that poker show, despite A.J. Benza. It's a little more offbeat and fun than the usual tournament shows.
Greed never dies, does it? (The show, not the vice.) This show has always been a personal favorite of mine, an interesting quizzer that deserved a better fate. It would be nice if GSN could pursuade the rights holders to allow the network to make an original version with lower payouts. The show is obviously a placeholder, but your guess is as good as mine as to what will eventually fill the place.
One thing's for sure: the schedule is now the most traditional it's been since GSN started broadening its programming two years ago. The schedule, including prime time, is completely dominated by traditional studio gamers.