99 times out of 100, $10 for 10k impressions is a rip off, depending on the site. Run-of-network ads these days are going for as low as 10 cents CPM (cost per thousand) the more targetted you get, the more quality site you advertise on, the more session aware, the more geo/network targetted, the more the price goes up.
With the exception of the "Big 3" (Yahoo, MSN, Google) you should be able to get quality advertising (with results) for less than $1 CPM, but you have to know where to buy. Targetting is everything.
If your worried someones site isnt going to produce any results, tell them to run your ad as a cost per click, or cost per action, so you only pay if the ad produces results. and you better track clicks on your end, so they dont rip you.
PM me, I got mad knowledge in the Interner Ad market.