You should feel lucky that they even offered you $100...
SKS's are a dime a dozen, and nobody wants them...
Did you think you were going to walk out with a different gun and only spend $7 for the difference ???
We get customers in all the time that remind us of what they paid for thier gun when it was new, or when they originally bought it...
Why would they pay you top dollar for a gun which they probably already have 4 of in stock, and can buy for $89 all day long ?
(Try looking at a dealer invoice sometime)
I could understand your frustration if you had "just" bought the gun, and wanted to return it, or if you were a "regular" customer that came in 2-3 times a week....
BUT, if you bought it over a year ago, and only put 50 rounds through it, you obviously are NOT in the gunshop very often...
You were lucky to be offered $100...
Many shops won't even take guns on a trade...
Not trying to offend you or flame you, just offering a "reality check"...