Look at the Star Trek models, Paramount Pictures hasn't shut them down. I don't think they can! Or they don't care. Again, this probably falls under fair use.
Yeah, but if I would use a Creative Commons license with "by", they would at least have to mention me as original artist of the model they reproduced.
Even if they can legally sell it for they did really enough own work, and it is maybe a good way in my intent to see my model represented (contrary to appearing in crappy B-movies).
I suspect, the better question is: Could they have done the model without my design? Sure not, they can't claim they have suddenly invented something new, that has all the traits of my design.
I think an email to the original designer and at least mentioning who designed something in the shop would be the minimum. It is not that much about money, I am pretty sure many add-on developers would actually love to buy one of their own designs from them, but I suspect that the shop would actually have to pay license fees, since they are not fulfilling all fair use criteria. Companies like Revell need to pay serious money to Warner for using their trademarks, and you still need to assemble and paint the stuff yourself.