In the vast majority of casinos across the world, the effect would be minimal, simply because counters operate with less than a 2% advantage with optimum play and conditions. If you take into consideration what percentage of high rollers (let's say $50 or more avg bet) there are in the total clientele base, and then take the percentage of those that are true winning card counters, you come up with a small number, and their total dollar amount put into play would be a small percentage of the casinos' drop. So even if your casino was being hit consistently with pro counting teams, it would barely show up in the bottom line, unless, of course, a professional card counting convention happened to land inside your casino!!!
The example where card counters could effect a
bottom line signifcantly would be a small but high stakes casino, much more seen
in Europe than in the US. There, card counting teams can cause casinos losing
days or even several days running.
Another thing worth
mentioning is that other types of advantage play, although much less common than
basic card couting, would effect the bottom line much more, given there was an
ample volume of these sort of plays.