In Canada - Ontario; Capital gains is taxed at 50% of the earned capital. it went down considerably a few years back from 75%.
With that said; if one invests $1000 and earns $1000 in capital gains (total $2000)
50% of the gain is taxed. So one needs only to pay tax on $500

The required tax to pay on the $500 is determined by ones marginal tax rate which has a tiered structure combining federal and provincial tax.
the marginal rate is between lowest 20.05% (up too 45k income) - highest being 53.53% (over 220k income)

the max tax on the $500 would be $267.65

(income is not determined by or inclusive of the capital gain one earns.)

I fall into the 0-45k income bracket so I would be paying just over $100 tax.
Minus all my capital losses over the years I most likely will be paying nothing in capital gains tax if I were to sell this year.

I don't mind paying back 100k if I earned 1 million in capital gains.

sounds like a pretty good deal to me up here.