Hey Nekky! Neat question you've got here - we had a quick huddle, and have agreed that it would be entirely possible for Hiccup to sell Toothless' shed scales. They would have both mundane and magical purposes, and it wouldn't be considered tacky. The fact that a dragon (even if it's not a Dragon) is willing to share their scales with them like this would actually be the opposite of tacky to them.

He'd find the best prices to be with smiths of all varieties, magitech builders, and witches seeking them for ingredients. He'd average 20000C to 30000C a pop for them, in notes unless he specifically requests coins, so about 181.34 to 272.01 USD for reference. And yes, by "a pop," we do mean this is the price per scale.