if you do a robots nofollow, wouldn't that be treated the same as though the nofollow were on the links
It should be, that is correct. It also nofollows all the internal links though those few pages might not cause a "site-side" ranking drop by losing those links, if the pages have a little PR, I wouldn't nofollow them out of the "loop" as it were.
What @Sgt_Kickaxe didn't mention was, What percentage of the links on those pages are affiliate links rather than related outbound links and internal links.
What @Pjman mentions about "noindex gets thrown out the window" - I've seen that happen to pages before updates, like pages you add noindex/nofollow go from PR 2/10 to PR x/10 in two days time. Think that's funny? Same pages with the noindex/nofollow removed get their PR back after 2-3 days. Can't guarantee you'll have the same results or get the PR back if you try that experiment, it scared me.