Why does Fishbowl say "Unit cost must be at least 0."?

You've entered a negative value for unit cost, which isn't valid. Unit cost represents the per-unit price you paid for inventory; it must be zero or positive.

Fishbowl: "Unit cost must be at least 0."

What it means

Fishbowl won’t accept a negative unit cost. In inventory costing, this field records what you paid per unit. A negative number would imply a credit or rebate, which doesn’t fit standard cost accounting and violates the validation rule.

What to check

The value you entered: verify there’s no minus sign. Re-enter it as a positive number or zero.
Decimal separator: confirm you used the correct separator (period vs. comma) for your locale.
Copy-pasted data: if you imported this value, check the source to confirm it’s not accidentally negative.
Whether zero is acceptable: if the system requires a cost, enter a positive value; if cost is optional, check whether leaving it empty is allowed instead.