How do mobile phone short message recharge manufacturers benefit from the game?

That's a good question ~ There is an agreement that mobile or Unicom customer service will recharge their business and they will extract some income from it ~ Let me give a simple example.

I sell cards, 5QB. I buy tickets in 3 yuan and sell them in 4.5 yuan.

The mobile phone company bought it for 4 yuan, and then deducted 4.5 yuan from your phone bill. He earned 0.5% from it, but this 0.5% is pure profit, and there are various handling fees, so they are also card dealers, but the trading platform has changed.

Give it to me for the sake of so many words ~ it's been a long time ~