You have to remember that stores get fish at wholesale prices, so probably about half (or less) what they are selling them to you for (depending on where you are). I would say $30-35 store credit for an adult Koran is reasonable. They can turn around and sell it for $60-90. The distributers are getting them as Adults for $8-12.
I agree with the Craigslist idea. You should be able to get more, you just have to deal with all the CL
flakes that say they are coming and never show.
That Hawk is probably reef compatible, but they can be aggressive. Something to consider depending on what else you plan to get.