You're right, but I think you're less likely to buy extra at per-unit pricing (since you can always buy just-in-time), so you're less likely to run into a situa

You're right, but I think you're less likely to buy extra at per-unit pricing (since you can always buy just-in-time), so you're less likely to run into a situation where you overpurchased at per-unit pricing. (Edited to note that.)