I've had similar experiences. I have a few browser extensions and other similar tidbits that I've built, and every now and then I get an email with an offer to sell it for a hundred bucks or so. Sell full scripting access to every user who installed something I made over the years? It makes me sad that that's the kind of world we're in, and sadder still knowing that surely there are people somewhere out there who do accept these bids.