Kroger, Walmart, etc do not deliver for free. At least not that I see. Also, they are all notorious for leaving items that need to be in the fridge on the shelves. I have heard that first account from both CMs and people I know that used Walmart and Instacart.
Kroger has run a set of deals twice for free delivery on your first few orders, but after that you are correct it is, 8 or so dollars. Walmart is free for me, and Whole Foods was free until this past year and is now 7 or so. None of those mark the items up and Kroger doesn’t allow tips. The only errors I’ve ever had with those deliveries is with bell services misreading a bag and leaving perishables out, so that’s on them not Whole Foods.
I like to support small business, but a markup like that is insulting.