Blades seem expensive and it's awful when you just replace one and then nick it. But along with sewing machine needles they are one of the best, easiest, and ultimately cheapest way to help improve our projects. I know this and I still let it go too long before I change my blades. I try to reduce the cost and the likelihood of me actually replacing them and buy them in multi-packs.
I have a sharpener thing too, I find it largely useless but wonder if maybe it would be just the thing needed for the new cheap blades that aren't working well.
A few years ago, I was able to buy some cheap terrible handled rotary cutters on sale for about $3 each, I took out the blades from them and put them in my regular handle and threw away the plastic...