> When I buy something, it doesn't cost my employer, it costs me.

If someone takes something from you by force and spends it, they're spending your money.

> as its "not other peoples money" is a monetary system that the government lets us use

The government doesn't "let" us use it. If we don't use it (e.g. by swapping services directly) then the government gets annoyed and tries to insert taxable transactions into that direct value swap. It makes us use it.