That's a very wild guess. I can only speak for LCS and OGN, since they're the only leagues I watch, but you'll usually get something around 30-40 games per patch.
Still, I'm kinda bored atm, so here are the actual stats for those leagues.
Since the beginning of summer split LCS, there have been 139 games played in NALCS, EULCS, OGN Champions and OGN Masters. Lee Sin has been banned 46 times in those games - curiously, ~half of those bans were on 4.9, despite the patch accounting for ~a third of competitive play. Lee has been played in 84 of those games as well. This gives him a total pick/ban rate of 130/139, or 93.5%. For perspective - Jax has a 81% P/B rate, Kassadin has a 97% P/B rate, Twitch has a 77% P/B rate, Thresh has a 75.5% P/B rate, Lucian has a 84% P/B rate and Elise has a 78.5% P/B rate.
Interestingly, 4.8 is the only patch on which Lee Sin has a winning record. He had a 44% win rate on 4.7, a 36% win rate on 4.9, and is currently sitting on a 50% win rate on 4.10, as I mentioned earlier.
Now, if I were silly enough to draw conclusions from such statistics, I would probably see that Lee Sin does not tend to win games disproportionately, and that he has a relatively low ban rate, and conclude that he's not relatively powerful compared to league champions in general, but possesses qualities that make him particularly desirable in competitive draft pick. Perhaps he's a very safe champion to blind pick, or perhaps other champions that compete for his role are astonishingly lackluster, leaving him as the most viable choice in most situations by virtue of his peers sucking.
But wouldn't it be silly of me to try to draw conclusions from just over 100 games, played over four different patches? Especially if I were trying to use those past four patches to decide how powerful Lee Sin will be on a future patch that I haven't even seen yet.