One of my current goals is to re-learn how to swim and bike, and do some triathlons. This requires not only some research into technique and dedicating more time to training, but also an investment in a lot more equipment than running requires.
Well, running doesn't require much in the way of equipment, but that doesn't mean there isn't a lot of optional stuff to throw money at. If I found all the transactions in my Mint activity, it looks like over the past year I've spent on running:
Clothes & accessories: $950
I'm grateful to have a well-paying job, but I'm not so great at budgeting, and really shouldn't be spending that kind of money willy nilly - that isn't going to help me meet other, bigger goals. Now that I'm adding two additional sports - ones which actually do have some need for equipment - I need to rein it in a bit. This is true for a $20 water bottle, $50 sports bra, or $100 shoes, but especially true for a $500+ bike.
I decided before buying a bike, I'll do some cycling on the stationary bike in my apartment complex's gym. Every mile biked = a dollar earned to spent on a bike and related stuff. Earned the first $6.50 towards the bike last night!
I figured I should do the same with running to keep myself on a budget. Making it retroactive to the beginning of the month, I'm already in the hole $60, since I registered for some races. Whoops. Better get some miles in...