If it’s likes BJ’s you need to not select BJ on instacart directly but instead use their direct site which appears to be a white labeled Instacart service, if you want the wholesale prices . In this example it’s https://delivery.bjs.com/ vs instacart.com.

They scrub most evidence of this being a white label service but it’s the same ui/ux and even the favicon is the Instacart carrot as of the time of this comment. Last time I compared my households ~$300 bill on the white labeled site was ~$450 on the main Instacart site