I'm certainly not a top graduate - I eked out of university with a 72% average. Neither are the other Canadian expats I know who are pulling this kind of cash - all are smart and hard-working, but none were among the top of their classes.
$110K 3 years out of college, at least in the current climate, is not at all uncommon in either NYC or SF/SV. It is not universal, but it's not rare either. If you look at the major investment banks, the institutional tech companies (see: Google), and the startups in NYC, this is the going rate for a mid-level engineer (i.e., $100-140K base). Hell, I have trouble finding fresh undergrads starting below $90K in these areas.
The point is, someone who is skilled at programming right now and has a few years of experience under their belt can very well pull at least $120K base, and even adjusting for cost of living differences, that's a hell of a lot more money than you can get in Canada.
In any case, this somewhat distracts from the point - it's not just about money. Myself and many other Canadian expats do not feel we can go back to Canada without working for the likes of SAP, IBM, TD, Royal, or any of the vast number of institutional enterprise companies that pound out rote, uninteresting code. There are some companies in Canada doing interesting work, but they are few and far between, demand for these jobs is intense, and job security sucks (after all, what incentive is there to treat you well when the employer knows they're the only interesting game in town?).
Compare with the SF/SV/NYC/SEA, where you can't throw a rock without hitting a row of innovative, interesting tech companies doing interesting things. We are hacking on interesting, immensely impactful things here, and we enjoy tremendous respect and security - after all, if management starts screwing around you hop down the street and go do something else that's interesting. The Canadian landscape looks incredibly bleak in comparison - a small handful of elite shops that everyone's clamoring to work for, and a vast tundra of code sweatshops where the problems are as uninteresting as the salary.