As soon as you descend into spreadsheet economics for punting you may as well quit, it's not a game with a positive NPV.

Just spend what you can afford at the end of the day, and what that will be will be highly subjective to the individual.

I do wish more punters on here got smarter and saved money and travelled overseas annually for whoring expeditions, as opposed to paying domestic rates for a much more substandard service. If more people did that, it would force the domestic market to change as a result. The approach requires discipline because you're trading domestic frequency versus a stack over 1-2 months, but if you actually perform both operating models I bet you'll come out the other end saying the overseas method was far better.