$299 is still ridiculous when you can buy an entire PC for that, but you have to expect to pay through the nose with the Mac. PC Hub? $25. Mac hub. $299.
The only "PC hub" you'll get for $25 is a USB hub that shares one of your computer's USB ports between multiple USB sockets. One generic chip, a handful of capacitors and some wiring. If that's what you want then, good news, because the vast majority of those will work fine with a Mac anyway.
A thunderbolt dock has a Thunderbolt peripheral controller chip (plus all the supporting gubbins for charging, Thunderbolt/USB-C passthrough and displayport) driving an internal PCIe bus driving full-blown controllers for USB, sound, Ethernet etc. (all of which needs drivers to be tested, if not writing). It's pretty complex, custom circuitry - and the potential market (and hence sales volume) is fairly limited. Volume, and economy of scale, is critical in the cost of electronics.
The reason that you can buy a complete PC for the same price is that a PC can be easily thrown together from whatever generic, mass-produced parts you can find in a bankruptcy sale this week, safe in the knowledge that they'll all come with Windows drivers.
That said, before we all start bleating and proffering our credit cards, these docks
should be a luxury item for people who can afford $300 to avoid the ignominy of having to plug in more than one cable when they sit their laptop on the desk. However, Apple's
courageous genius in stripping all the useful ports (including power) from their supposedly "pro" computers has made them something of a necessity: take a non-TB MBP, plug in the charger, plug in an external display and, sorry, that's you're lot! C.f. the Macbook
Air (forget the old 'pros with even more ports), to which you could connect the charger, an external display, a USB keyboard or mouse, a USB backup drive and a SD card before having to reach for hubs/docks.