I don't think tolls are tools at all, they are the results of privatization of infrastructure.
Cross harbour, which I used just last week (went to pick up furniture), is a disaster mainly due to poor infrastructure planning. So many roads leading into a bottleneck of insufficient toll booths that then lead into, an even worse, very short run off back into a 2 lane tunnel. Why they don't even have the old school change baskets vs. humans here is beyond me? Eastern tunnel is worth the extra distance not to sit in a parking lot for 15 mins. Western tunnel should be equalized to the others but they're all overpriced compared to regional cities I'd imagine.
I can't compare HK to Canada where tolls are extremely rare, or the even the US where they are more common but reasonable (save Manhattan) so I'll compare HK to Korea.
In Korea average yearly registration, inspection, and taxes are about $200USD for 2.5L car, here $1000USD (after a 30% hike). In Busan they built: nice new bridge, tolls at the time cost a whopping $1.00USD, the highest around compared to all the tunnels and expressways which averaged about $0.60USD. Several of these tollways have since become FREE (as promised by city) and they've even built several new tunnels + bridges (they're a bit nuts with the infrastructure), still no where near the costs of HK, and of course conceived and built in years not decades.
The costs private car owners pay here likely exceed the pathetic upkeep of the infrastructure in this tiny SAR, and the road conditions are far inferior to Korea and likely other comparable Asian countries.