Why is it so hard for you people to look at what is actually happening? Nothing is sold. Factually, the system just plays with the numbers according to some protocols. Can you comprehend the reality of that? Nothing is sold or bought in your example. People sell and buy liabilities in the banking system. Liability is the type of money. Operation with the numbers in the banking system means quantifying liabilities. Liabilities are existent things in the banking system and are quantified with the numbers. In the Satoshi's system there are neither liabilities nor some other type of money. Only fake quantities. These quantities fool many people by creating the illusion that something exists. That something is quantified with them, like coins. But it's not. Quantities are fake.
Oh, you are still here? You still didn't give up? Damn you are one stubborn person...
First, stop comparing Bitcoin to fiat money. Fiat money represent (or at least should represent) liability as you say. Bitcoin does not represent anything. If you need something to compare Bitcoin to then use gold as it is more similar to gold than to fiat money. The only difference is that gold is a physical thing and Bitcoin is not. But you can't say that Bitcoin doesn't exist because it exist. It is a digital data that is generated to reward system that solves complex mathematical calculations in order to verify transactions.