Over the holidays, oat milk, and specifically oat milk from Swedish company Oatly, has been one of the most sought-after gifts. And in response, some folks are selling it on Amazon (AMZN) and elsewhere for more than $200 to capitalize on the craze and make some money on this year’s hottest holiday gift.

Oat milk has actually been around for years, but became an international sensation this year. According to Oatly, its milk is a “vegan, plant-based milk alternative” that’s made from gluten-free oats. The oats are milled and separated and then Oatly adds a variety of ingredients, including sea salt, vitamins, and cocoa powder, to create its many oat-milk-based products. It then pasteurizes the milk to extend its shelf life, heats it in a sterile tank, and sends it off to stores, where it sits on shelves next to traditional milk.

Oatly’s products, which include a chocolate milk version and one designed for baristas, have taken the world by storm. In fact, if you head over to Oatly’s site today, the company’s Barista version for coffee is out of stock.

Given that popularity and the fact that oat milk is so hard to come by, people have bought Oatly products at their retail price and quickly put them back up for sale on Amazon at significant premiums. For instance, one seller on Amazon is selling as 12-pack of Oatly’s Barista Blend for $226. A six-pack regularly costs $25. Similarly high premiums are being charged elsewhere Oatly is available.

There’s no telling when the oat milk craze will cool and prices will come down. But all signs right now are pointing to some hefty pricing on oat milk through the end of the year.