LCranston’s math is correct. A $20-$22 utility knife system will last a long time. The Milwaukee Utility Knife he mentioned looks like it would work well, I like that the blade can function as a hook knife and it has a cut-out to work as a wire stripper, nice touches. The Husky I linked to earlier is slightly less $$ (neither are expensive) and both are available at Home Depot.

My recommendation would be to check out Home Depot or another local Hardware store to look/touch before buying; if you see one you like, buy it. Do not start a utility knife collection, just buy one that works. The replaceable blade are pretty much standard across the different brands.