[Stone Mountain]

If Bill plays the high limit slots the return is around 96%. For every $1,000 fed into the machines he would lose $40 if he played for 50 years.

The "if he played for 50 years" doesn't really make much sense here - are you using it to imply odds over the long term? In any case, you are correct that he would on average, lose $40 for every $1000 he risks. In the case of high-limit slots, It is very easy to risk well upwards of $30,000 per hour (for instance, look at $300 per pull which is conservative with high level slots, and 100 pulls per hour which is also quite conservative) which equates to an average loss of $1200/hour. With multiple machines and multi-paylines, this easily gets multiplied.

If you add his comps into the mix, his enjoyment may more than warrant his gambling "vice".

His comps are small potatoes compared to what he is losing - casinos make their money off of high rollers like Bennett. If you want to say that Bennett is rich enough to lose a bunch of money, I don't have a problem, but saying that he's getting over on the casinos with comps and his enjoyment of losing a bunch of money is lunacy.

[Kahuna]

Yes and sorry, I was implying that the return percentage is over millions of spins. A random generator number in the chip determines the win/loss for each spin. You are also right that playing $300 a pop dramatically raises the casino hold.
Statistically, video poker would be a much better play for a skilled gambler using his loyalty card and taking advantage of comps.