Front panel usually just has the headers (the connectors), with wires leading to the USB controllers (the chips that do all the USB functions) on the computer's motherboard.

So ultimately all costs are NOT equal, the USB chip may be able to control only so many USB 3 devices, but a lot more USB 2 devices, so a company may put a lot more USB 2 headers on the front panel than they could USB 3 headers.

There is a data bandwith limitation. And there's a chip shortage / chip cost limitation too.