Yep, I think you're right. I saw some smaller samples of loctite 242 here...
Locktite 242® Threadlocker
If you sourced all the parts I'm pretty sure that $12-$16 would be more like it.
If you added a plug, maybe get somebody to even donate some two-stroke oil samples, an inline fuel filter, and a #41 chain and you're talking maybe $30.
You could offer a whole kit or whatever anybody wanted. As long as you kept the prices reasonable, folks would probably prefer to one-stop shop rather than having to hunt it all down separately.