Your giant programs with community and district support (Lake Travis, etc) sure. They can cover that. But you get down to A, 2A, 3A schools...they recondition helmets yearly. They send them in to get checked out, and if they pass, they can reuse the shell yearly (up to 10 years). If a helmet ever fails, then it has to get scrapped.
So, a small school like that might budget for a dozen helmets a year, with reconditioning for the rest of their inventory. Yes, they could make up with pie suppers and other fund raisers, but schools generally just don't have that kind of cash flow to purchase 50 helmets a year. Source: I've had two former head coaches live down the street from me. In the 90's, it would cost around $400 a kid for football. Today, game pants are around $100 a pair, and jerseys around $70 each. That's for something simple. You want to look like Oregon? Or go with sewn on numbers? Prices are going to go up. Helmets and shoulder pads have gone up quite a bit.
Now, I have no idea of the size or district/community support of the school that Mayfield made the donation to. But they needed the donation. And there are hundreds more schools like that coast to coast.