If someone is selling a item to be used for a money making enterprise i.e. mining there is a understanding that is implied to the client that this service will make you money NOT COST you money your excuses are all bullshit.
Nobody with a dollar is going to sell it to you for 80 cents.
If someone is selling a service to be used for money making, there is a clear understanding that is implied to the client:
They're going to make more money selling the product to you than they expect to make using it.