"Sells itself" means the product able to stand on its own and raise awareness without paying for advertising to do it.
You of course need people to sign contracts & complete the purchase, that's irrelevant to how well the product is able to raise awareness without advertising, i.e. people interested in buying Tesla's didn't hear about it through any of their advertising.
You of course need people to sign contracts & complete the purchase, that's irrelevant to how well the product is able to raise awareness without advertising, i.e. people interested in buying Tesla's didn't hear about it through any of their advertising.