If something is not profitable enough, then that is still a form of charity. For example, suppose that my market rate is $50/hour. An organization tells me that they could really use my services, but all they can afford to pay me is $10/hour. If I accept their offer, then I am essentially giving them the equivalent of $40/hour in charity.
Based on your first example, I don't think you understand what "charity" means. It's not an imposition, as you imply. If you lowered your price it would mean that you took $40 of value in some form other than immediate monetary compensation. Whether it's a public relations coup that you think you will benefit from at a later date, a warm fuzzy feeling inside, or the reduction in stress from knowing that you won't be inconvenienced while checking out with a credit card because of slow internet, you will have found some offsetting value.
If it's just a reduction of value imposed by the government, it a tax, a fee, or "taking". Charity is not coerced.