Saying a taller building costs more to build is a statement of fact, not a statement of opinion. That's why your comment did not make sense.
Maybe I should have rephrased my original statement. Taller buildings become less profitable the higher you build. I think I read somewhere or heard from one of my old professors that once a building gets to about 90 or so floors, it barely breaks even (construction, maintenance, leasable floor area, vacancy rate vs. revenues in rent).
Of course you mentioned only "56" storeys for this site, but it does have it's challenges. I first mentioned skinny because I thought the site was relatively small due to land constraints between the rail the corridor and Bremner. Therefore to get a 56 storey buildng with the same leasable floor area as Telus and 18 York combined, it would have to be a skinny building. There are more forces acting against a building that is 56 storeys than a 30 storey building such as wind and loads. This will require deeper foundations and materials that can handle the structural requirements to offset these forces. There's also the rail corridor with the hundreds of trains that go by everyday causing vibrations that would have to be addressed, again through structural engineering and materials. The loss of revenue due to extra elevators required, as nstuch mentioned, is another loss.
But, I'm not going to debate this anymore. You're of the opinion a 56 storey building and a parking lot (if not a vacant, fenced off dirt field) is better; and I feel a 30 and 26 storey building that both provide quality streetscaping and are more appropriately scaled for these locations are better. To each his own, just don't twist my words around. And for the record, I love tall buildings, but in the right location.