In Expenses the first tab is custom costs: one-off, weekly, or monthly amounts in your store base currency. Weekly expenses are spread evenly across 7 days (amount ÷ 7). Monthly expenses are spread evenly across each calendar day of the month while active (so servers/SaaS do not create a fake cliff on the 1st). Saving recomputes daily profit from that date forward.
What counts as custom expense
- Hosting/server, SaaS tools, salary allocations, warehouse rent, agency retainers
- Not COGS (use Products) and not carrier cost (use the Shipping cost rules tab)
Payment method costs (default % + fixed, and per-method PSP fees) are the third tab: Expenses → Payment methods costs.