My understanding is that Thunderbolt no longer carries royalties; it’s just that it’s plain expensive.
A dual-port Alpine Ridge controller(and the new hotness Titan Ridge is $9.10) has a stated tray price of $8.55; and it’s not a Thunderbolt port unless it has 4x PCIe lanes and DisplayPort; so that would take you from a SoC with a PCIe lane to hang the USB from, plus HDMI presumably in keeping with Broadcom SoC’s set-top-box legacy to something with at least two DP outs and 8 PCIe lanes dedicated just to video.
USB-C alt modes at least dispense with the PCIe requirements; but would likely still require using newer USB silicon than they did; which is more costly than doing the exact same thing but with a different physical connector.
None of the above makes me a fan of micro HDMI; I’m distinctly not; but by contrast it looks like a micro-HDMI connector costs 4-5 cents more than a standard HDMI connector in quantity(possibly a smaller difference in larger quantity; but the gap is pretty narrow even in the several hundred to a thousand range) and requires no change in chip capabilities.
