How do I project the income of each bed in my market garden?

Multiply what a bed gives you by what you sell it for, once per crop, and let Heirloom carry the numbers into your whole season. In the Crop yield chart, enter for each crop the unit you sell in, the yield of one bed and your price: the revenue per bed is calculated for you.

Every new planting takes those numbers, and its Harvest And Revenues tab shows its Total Average Revenue. Your season’s forecast is built from your own figures, so you can see before you sow which crops earn their beds.

Use your own harvest records when you have them: they are worth more than any average. Yields are read per bed of your standard length; change the Bed reference length in Settings to read them on another length.

The steps are in Set your yields and prices.