Maybe pwg is right and the discounted price with Windows is due to the paid pre-installed software. But that still leaves the customer with complete freedom to install something else on it.
Some people want their laptop to work out of the box, and will happily pay $200 to ensure they get a HW/SW combo that’s been validated to work together by the manufacturer.
If you’re a company buying 10+ laptops, paying an extra $200 per laptop is probably cheaper than the faff of separately finding and acquiring wifi cards, then finding the time to swap them all.