Google Ads success requires knowing your ROAS (Return on Ad Spend) and true ROI after product costs.
ROAS = Revenue / Ad Spend. A 4× ROAS means $4 earned per $1 spent on ads.
True ROI accounts for COGS: if product margin is 40%, you need ROAS > 2.5× to profit.
4:1 (4× ROAS) is a common benchmark. But profitable ROAS depends on your product margins.