Google has a "Purchases" page that shows your purchases based on receipts you have in your Gmail inbox; Google says only you can view your purchases (CNBC)

CNBC:
Google has a “Purchases” page that shows your purchases based on receipts you have in your Gmail inbox; Google says only you can view your purchases  —  KEY POINTS  — Google saves years of information on purchases you've made, even outside Google, and pulls this information from Gmail.