Certain sites may be selling sh1mmer or bundling it with purchases. These sites typically claim to offer many features for your chromebook, while in reality they just provide a collection of freely available software, illegally.
The sh1mmer recovery tool is strictly distributed as a free download from this website. Any kind of sale, bundling, or redistribution in association with commercial activity is strictly forbidden and a violation of copyright. Don't let them scam you into paying money for free stuff!
If you have clearly been sold this software, you should report them to their payment processor (often ClickBank, Plimus, or PayPal) and demand your money back. Keep in mind that this kind of sale is illegal (selling our free software is a violation of copyright) and also fraudulent. If the payment processor refuses to issue a refund, contact your credit card company and request a chargeback.
(disclaimer: not an actual legal statement)