I charge $3.50 for tomatoes or 3/$10. Peppers and eggplant are $3 or 4 for $11. yes peppers and eggplant should cost more than tomatoes due to starting earlier but I don't do it that way= it all evens out anyway.
Those are like 3-4 in. square pots. For smaller plants in multipacks they will be $4-6 depending on quantity. Herbs and small annuals and small perennials are usually $2 in small square pots or peat pots. Larger potted perennials are $5.
I am doing peat pots of 3 squash or melon seedlings, as a hill, for $4. Maybe that is too high? I have also had some luck selling potatoes or sweet potatoes in bushel baskets with soil. But they are a pain to bring to market. I have not had luck selling very large tomato plants so I just grew them for myself this year.
I have had little luck selling eztra seedlings like leeks, scallions, brassicas and so on. But this year I have 2 cute shallow wooden trays with nice lettuce plants in them. I think I will put a high price on them and see what happens. If it isn't heavy and a pain to bring to market I will price it higher and may bring a few weeks just to see.