While that can be bad, sometimes you come out ahead after accounting for spoilage, time, and travel.

Sometimes I pay higher unit prices at a dollar store intentionally because they offer smaller package sizes not offered elsewhere and I only need the smaller amount. I could get a much better unit price at another store but would waste the rest of the product.

Speaking of travel, that's why I go for them.

If I'm going for a multi-day stay somewhere and I don't want to deal with annoying mini bottles of hotel soap, I'll just pop into a Dollar Whatsit for a small bottle of something suitable at my destination.