About six years ago a mate of mine here fell on some hard times and I agreed to loan him a not-insignificant amount of money as long as he promised to stop sport betting, seek counselling, allow a mutual friend (who was a CPA) to take over his finances for a year whilst he paid me back, AND he let me get all of his betting slips from the last 10 years (he only bet on three big online betting sites, each with exceptionally good record keeping).
I ended up spending a few weeks tabulating his bets, putting together a P/L for the period.
Once all was said and done I was able to show he would have +$82,000 if he simply didn’t bet, and around +100k if he had just invested the money in an index fund.
Fortunately, the counselling and professional accounting got him off it, he paid me back (interest free), and is doing much better now.