There is a bit in Konmari about saving things for best. The whole book might be worth a read, I think it does come from a sort of hoarding mindset and I think the Konmari method is a good antidote to hoarding without being all "Minimalism is morally superior" which I usually hate. It definitely struck a chord with me - I found some old art/craft stuff that I had as a kid and "saved for best" - by the time I looked at it, I was all grown up, and while I could certainly appreciate that it would have been nice to use, I didn't have any urge to use it any more! And as an adult, if I wanted rainbow transfer paper or really intricate puzzle pad pages, I can just buy more
I gave it all to DS1, who was about five, has nothing of my saving for best mindset, and used it all at once. I think that was sort of the lightbulb moment for me.
The thing is if you're denying yourself the thing now, you are no better off than if it's all gone because you've used it (or "wasted" it) - so in fact you might as well just use it. Then at least you've HAD the pleasure or enjoyment out of using it. That's what I tell myself, and I make sure to enjoy it when I do use it! The sparking joy thing from Konmari really does help with this, I find.
Also, even though we are fairly tight for finances, it doesn't mean that everything nice is absolutely impossibly out of reach and will be forever. If something runs out and I want more of it and can't afford it straight away, all I have to do is save up. It might take a long time, but eventually I will be able to have that thing again.