Are you talking specifically about Quebec here? This kind of thing varies a lot by jurisdiction, but in many jurisdictions the high costs for a plate are not paid to the government, but paid on a grey market to a prior owner, with the fee for registration being nominal except for the fact that no one gets to register any more. In many cities (including mine), people own plates as a retirement investment and are fighting deregulation because their investment will crater.

Not that this is any better, but people talk as if there's One Way taxi regulations work all over and there's quite a wide range on these things.

Also, the nominal reason for limiting plates is usually (as far as I've ever seen) to ensure a living wage for taxi drivers. I don't think it really works out that way, instead creating a class system where some people extract rent from other people.