$25/week ($50 per paycheck) goes automatically to a hobby spending prepaid credit card. It's my personal allowance. I sneak some ammo purchases into my household shopping since it's one box here, one box there, from places where I find myself buying other things like Crappy Tire and Walmart. I don't shoot more than a box a month so it slips through. If I buy from the LGS though, it has to come from my allowance. It works out to $1300/year, which means I can buy a cheap rifle every few months, or a nice rifle every year, or a higher end gun every few years.

It is self-imposed so that both my wife (she's a stay-at-home mom, no income) and I can both have a dedicated hobby allowance so that our credit cards don't creep up. We've been there before, $6k on each of two cards demolishes the disposable income we have with minimum monthly payments. So this way our credit cards stay at $0 and we don't need to beg each other or justify our purchases because it's money earmarked for "Undisclosed Discretional Spending" as I like to call it.

Aside from that, I keep ourselves in a simulated "broke" state by putting almost all our disposable income into savings right off the top of my paychecks so I never see it. We're not good with money so making sure we have to go through a process to access it is a great way to take the impulse out of things.