Description from extension meta
Check LEGO retail prices from the US store by selecting LEGO IDs on any webpage
Image from store
Description from store
You can select or manually input any LEGO ID to get the retail price of any LEGO set.
If you want to check a lot of items and you want to keep the extension open, you can pin it to keep it floating on top of the chrome tab you are working on so you can check multiple LEGO IDs quickly.