I buy mine from ebay. Cheaper than Sally's and a fast service
As professionals we do not ever promote the purchase of products from Ebay here on this site. Too many have been 'burned'!!
There are many reasons why a professional would not buy from this source, not the least being that you have no back up from a legitimate distributor.
The products are not always legit as to what is in the bottles, and
you are knowingly buying products that have been imported into the country totally illegally as OPI and other brands have exclusive contracts with legitimate distributors who are here to train you, to supply you, and to support you.
Something cheaper is not always the best reason to buy it!! We make good money as nail technicians buying at the normal wholesale price. I do not believe it is always cheaper either, in fact I know it is not.
Another reason is that the ebay seller often posts items that are flammable illegally. Legitimate distributors follow the rules.
You have to live with your own conscience but for a few pennies saved, I would rather do things legally and correctly and safely.