Taxi medallion fell in price around 2011, because the government increased the supply (consumers started screaming about high taxi prices - and trust me, as a Sydney-sider, they are ridiculous, and the service is on the whole, pretty shoddy. I challenge you to find anybody who will defend Sydney taxi pricing, or their service).
You don't see the government compensating the taxi drivers for that - taxpayers would be up in arms.
It's only now, that they have somebody external to demonise, that they can get away with giving our money to them.
At the end of the day, nothing was taken away from the taxi drivers - they still have exclusive rights to pick up from ranks, and of course, can still operate as taxis. It's just, the digital age caught up with them, and they now have some real competition. A lot of the Uber drivers I spoke to, do this as a part-time gig (at least in Sydney) - they have a car, spare time, why not make use of it. Everybody wins.
Taxi prices have nothing to do with the availability of plates - taxi rates are fixed, not demand based.
Lower availability of plates would be linked somewhat to higher profits for taxis though (since it should increase their utilisation if the taxi is deployed in high demand areas).
Taxi plate owners did complain at the time the supply was increased (iirc saying mainly that there were already too many taxis), but there was little they could do other than make some noise.
I'm a Sydneysider and semi-regular taxi user, and given how far out I live from work - well aware of how expensive Sydney taxis are.
Tip for travellers to Sydney: after I complained about a trip costing $35 from the airport to Botany (could have been more, but I realised he was going the long ways early enough), one of my UberX drivers pointed out that the trick is to order the UberX right outside the airport (the bridge works), then phone the driver and arrange for pickup inside.
I'm not sure that the $280k pricetag is going to work given the changes (in Sydney, anyway).
The only advantage now that a taxi plate has is that they can stand at ranks, be hailed and operate at the Airport.