TikTok Shop sellers: do you actually know your net profit per product?

I've been talking to sellers over the past few months and the same thing keeps coming up => Seller Centre shows revenue, never profit.

No COGS field, no per-product margin, and payouts land 8-31 days after delivery so nothing reconciles by week.

Curious how people handle it. Spreadsheet? A paid tool? Or just going by feel and hoping the bank balance goes up?