Sky,
You are not making an even comparison.
Even though the tires are probably of different performance levels (I'm not familiar with Pirelli Motorcycle Tires - but I have had a bunch of their car products) you are looking at the cost of 2 tires, only.
Tintin has included 2 tires with tubes and rim strips. I don't know why he mentions rim locks, I have not seen them used on a CB500 or 550. Also it seems that he is including labor to mount and (hopefully) balance. Another thing to consider is the currency adjustment as the Canadian $ is not equivalent to the greenback although with the help of our politicians, it is closing fast. Additionally there are more taxes on this type of purchase in Canada.
I think that there may even a VAT on tires, but not sure. Is that correct TinTin?
Anyway seems like a pretty good deal.