A monthly premium pass (for riding buses, Trax, and FrontRunner) is only $190 per month, which seems fairly reasonable.
If you are commuting to/from downtown SLC, public transit is actually somewhat reasonable - I live in the southwest end of the valley and it is only maybe 50 minutes vs 35 to drive in ideal conditions. The bigger problems are:
1) The trains don't run nearly often enough. If you happen to miss one or need to go at a non-peak time, it is going to be really inconvenient.
2) Not only does much of our population live in suburbs, a large amount of jobs are located outside of downtown, too. In that case, a 20 minute commute by car can easily be a 1.5 - 2 hour public transit commute - I can drive to work in about 25 minutes, but according to UTA, the most optimal route by bus/Trax would take 1:30.
The way we've situated things here is pretty hostile to mass transit, but I'm glad we're at least making slow progress.