$240 is a very fair price. I've seen them for less than that, but I've also seen them for more. I have 2, both with wood stocks, one I got for $180 and the other (in better condition) for $210 OTD. I also have a 26" Black Shadow that I got for $190 OTD. I feel like I got a good deal on each of them, and I'm always on the lookout for more.
The big gunshop near me had a wood Defender marked at $279, it's not there anymore. They also have a Black Shadow just like mine, but in worse shape, for $299. That one's been there for a while. The going rate seems to be around $300 at gunshops, less for face-to-face.
The synthetic guns seem to get a higher price, so I think the price you paid is fair, and bordering on good.
I like my 1300's, I'm sure you will too. Parts are relatively easy to find and reasonably priced, with the exception of barrels. I wanted to get a 26" barrel for my Defender, and found that it was cheaper to just buy the whole gun. There's a very limited selection of accesories out there though, so don't plan on adding a bunch of extra parts.