This is true UNTIL you extend it on either end.
If the line is to be built out from Malvern on the east to Pearson Airport in the west; LRT is billions cheaper (capital wise) than the other options.
If the line stays exactly as planned today, with no expansions at all, then LRT is not the cheapest option. Basically, the expensive chunks are being completed now and we can do the cheap portions later pretty much on a 2% property tax hike which lasts a 10 year period (after 10 years property taxes drop 2% again).