People don't value their time like that, at least, most of them don't. I mean, some do, but at my hourly rate the time I spend on driving and shopping is much more than its cost and I still balk at paying e5 for grocery deliveries, and I program economic models for a living! (instead I always order a few products that give me free delivery, and/or select a not so popular delivery time slot).
Point being, economic modeling and naively assigning a time value equal to or even just related to people's normal hourly wages is - well - naive, and does not yield accurate representations of real world behaviors.
Here's another example: I used to have a cleaner who I'd pay e10/hour. She'd park across the street from my house, paid parking, e6 per day. There was free parking available at 10 minutes walking distance. So for 20 minutes of walking, she'd save 6 euros, i.e. e18/h, almost double what she could make from her actual work! And yet she continued to pay for parking, even after I did this math for her. Point being: people are sensitive to costs in very non-intuitive (some might say: irrational, but I don't like the connotations of that word) ways.
This is the problem - it's not going to be 'almost supermarket prices'. It'll be a 10-20% markup, which is a lot for food.