Coin exchange markets create the coin "out of thin air "
You first buy the 0.0001 BTC from Binance or any local coin exchange markets.
You give 3.5 dolar to Binance and Binance add 0.0001 btc to your account.
In this transaction, really, Binance gives you BTC ?

I don't think this going to work on a large scale because the bitcoin price is fluctuating heavily these days. I would be very careful if someone promises you a fixed Bitcoin amount over a longer period of time. Creating coins out of thin air is not really possible, somewhere there must be a profit being made by binance to give you such good offers.