It sounds to me like you've redefined 'consensual' to make your philosophy produce the results you want.

Both transactions were consentual and noncoercive. There were no threats of violence. An adult business owner signed a contract for services which were provided exactly as specified. The customer didn't have to agree to the first, poorly negotiated contract. And they don't have to pay extra for the extra services later on - it's entirely their choice.

It's no more extortion than if you need a new ink cartridge for your printer and you find they're expensive.

I put it to you that the situation I've outlined is unethical, even though it's consensual and non-coercive.