No matter what the per unit cost of producing a nickel is - it will probably go up when the mint stops producing the cent. Most likely all denominations' per unit cost will go up because they will have to absorb the Mints overhead and fixed costs previously allocated to cent production.
Good point, but the overhead costs will probably decrease considerably as well as they will be making less than half as many coins. A lot less dies will be needed, less labor costs, probably be able to cut working shifts. It will be interesting to see how the costs per coin changes, but we won't see those figures until 2027. We will get an idea how they change next year though as the reduced 2025 production starts shifting them in the 2025 mint report. If they shift enough the dime may be at risk as well.
Mint facilities: guards, rent, utilities, those are mostly fixed costs and will be apportioned over fewer coins. Labor &c are variable costs and will first show up as less OT. It takes time to rightsize a workforce, especially if you are cutting out half the work