Well one popular investment strategy, which is just to buy a few diverse index funds or ETFs and hold them, has no time investment. Of course the return for a blackjack bet is about 1 to 2 % over a time span of one minute, whereas the stock market investment should return about 7 to 8% annually. I guess the more accurate comparison would be what you could do with say 70k as a bankroll for card counting vs 70k invested in the stock market. So with the latter you might expect a return of say $7000 a year (optimistic projection) whereas the 70k bankroll could easily return 100k in a year but require say 4000 hours of labour.
Of course the two things aren't mutually exclusive. You could invest your blackjack bankroll (or winnings generated from it) in the stock market.