It looks like a reasonable price, if only you were a little closer.
I usually pay the asking price on 90% of the stuff I buy off of Craigslist. Sometimes I'll round UP to the nearest multiple of $20!!! Occasionally I'll offer less if it isn't worth the asking price to me. But, the seller can usually figure out if I really want it, and then it is hard to bargain.
Depending on what it ultimately is used for, the trailer will need some work. Perhaps different sides, a tailgate, FENDERS. Does it have lights? The ramps look nice. Perhaps take another photo to show the fenders & lights.
I assume if one is hauling something like bark, it still needs some shovelling, but it is easier to shovel downhill.
Also, I'd encourage measuring the bed and posting it in the ad. What's the thing in the middle of the bed? Attachment for the dump? How big?