If Wikipedia is to be believed then Sony opened up their E mount specifications in 2011 and there are 17 3rd party lens manufacturers that have signed up. 9 years is a long time for 3rd parties to build up native products and for their pricing to plateau.
There's no doubt that the lack of 3rd party lenses leaves a lot of gaps in the Canon's native RF lineup today. But if you combine the adapted EF and EF-s lenses and 3rd party EF lenses then there is a very broad range in price/focal length and quality. RF lenses L lenses are best in class (except RF24-105mm/4 which is reasonable) and have a premium associated with them.
Tamron/Sigma etc will make RF mount lenses but probably only the EF protocols so Canon natives will only make use of the 5 axis combined stabilisation.
Canon is playing a long game here any taking profits wherever possible to maintain fiscal viability. Sony really didn't have a choice back in 2011. They needed lenses quickly and couldn't do it all themselves and the only way to break into the Canon/Nikon body market was to have smaller and better specs (we all know their limitations) that meant that users could adapt existing lenses and a broad range of 3rd parties. Canon and Nikon did drop the ball by letting Sony carve out their niche. Ultimately, Nikon looks to be on the losing side at the moment.
With a declining market, profits have to be king and yes - we are paying them