[klempner]

Any currently existing (to say nothing of two years ago) "TB/USB4" chipset would dramatically increase the price of something with a retail price on the order of $50.

With that said, DisplayPort Alternate Mode would be considerably more straightforward.

[tracker1]

Apparently the RPi 5's SoC already supports USB-C display alt-mode.. unfortunately they don't to proper PD negotiation, which would not be considerably more expensive. There are cheap vape pens that support PD negotiation properly.

[klempner]

Are you sure these "cheap vape pens" don't just use 5V3A, which doesn't require any PD negotiation at all? (a lot of them screw even that much up, and a lot of people confuse "PD negotiation" with simply having the right resistors on the CC pins)

There is real cost savings here -- the RPi5 avoided the need for a buck circuit, and for that matter probably a dedicated PD controller chip.

In contrast, in the context of a "cheap vape pen" you have a battery which means you need to be able to convert to (and from!) battery voltage, so you need that conversion circuitry anyway.