Easy for them to build something technically equivalent, impossible to guarantee that it will get the same usage. There's a reason why companies like Google, Amazon, Apple do hundreds of acquisitions every year despite having enough money and talent to build it all on their own.

definitely cheaper to build the tech, but possibly more expensive by the time they've convinced all the stores include a "pay later with square" button. as always with these things, they're buying the market not the product.