[bunderbunder]

But not, I think, cheaper than a cab company setting up their own fleet.

Being a bigger player, a cab company is better-positioned to take advantage of what few economies of scale exist in this space: The power to negotiate a lower per-unit cost, and the ability to operate your own garage so you don't have to pay retail prices for maintenance and repairs.

The cab company would also be the more vertically integrated option, which gives them additional opportunities to economise and pass the savings on to the customer.