Margin vs markup
Profit margin = (revenue − costs) ÷ revenue. Markup = (revenue − costs) ÷ costs. A 50% markup is only a 33% margin, a common pricing mistake. To hit a target margin, price = costs ÷ (1 − target margin).
For solo freelancers with few costs, include a cost for your own time (hours × your base hourly rate) to see true project profitability.