Quick answer
Break-even units depend on contribution, not just revenue.
Break-even units = fixed costs / (selling price - variable cost)
If the contribution per unit is weak, the required sales volume rises quickly even when the top-line number looks attractive.
Use this after product cost is credible
Break-even is useful when the variable cost per unit already reflects reality. If the COGS figure is still optimistic, the break-even point will be optimistic as well.