I do things for myself that I like of course, but I am not sure if any of those things would be considered a reward, which I find interesting
Sounds like a great logic to justify stuff that might be considered "rewarding yourself" ;D
I am teasing mercilessly
I'm pretty much the same as you, stupidly expensive items years apart, and things that can be counted as "investments" (usually it's computer equipment for art purposes). Reward for saving up the money? XD
Rewards for other people umm the kids will usually get to pick either takeaway dinner (which is the option they will usually take) or ask J to cook something specific when they've done something exceptional (usually it's gymnastics competitions). Otherwise pretty much all I have to give is gratitude and trying to do nice things for them because spare money what's that.