From my limited experience working as systems for a large retailer. Thermal paper is more expensive, but the printers are cheaper and more reliable. It's not massive - I would estimate about ~20% difference - of course this can depend on print counts. Having printers down can have a much larger operational impact than the difference between types.
Does it cost more to print more black? Or is the cost of printing baked into the paper?
In standard printing white is free. Is the opposite (or cost neutral) true for thermal printing?