This was a very cheap set, bought specifically for this use.I haven't replaced a hole saw bit in many years. For a few bucks you can get a chain saw file or kit (Kit comes with a couple different sized tiny round files) and easily re-sharpen them. You just need a vise to hold the hole saw bit and arbor. You can also do it with a grinder with a cutoff wheel but that is a bit less, exacting. You won't get as many re-sharpenings out of each holesaw bit that way. Much cheaper than replacing bits especially the large ones which are not cheap if you buy decent ones.
There are quite a few Youtube videos on sharpening them.