5 oz of store brand bagged organic spinach at Whole Foods is $1.99/bag. The same amount of organic spinach of the same store brand in a clamshell costs $3.99/bag.
Are you sure they are the same amounts of spinach? I was at the store tonight. 4 ounces of spinach in the bag. Small clamshell was 8 ounces and the large clamshell is 16 ounces.
I am getting my prices from Instacart, so it's possible that they made an error. However I recall seeing this myself at some point as well.
I'm convinced it's a mistake on the part of Instacart. They are the same price at my WF. I don't use Instacart, but I do use Amazon Prime Now. When there was a weird price on Shiitake Soy Sauce, I called Prime Now customer service and they fixed it. If not that, then your WF is charging you $2 for the clamshell.
Whole Foods has never been known for consistency of pricing.
In fact for small uses of items for one or two people. It's can cheaper to use their salad bar for Spinach, and other light weight items (NO DRESSING!) for use in stir fries, salad mixes etc.
Maybe try it? Weight a bag of salad on the salad bar scales...do the math and see what happens if you got the same item as a salad bar salad? They count on you using dressing to boost the price.
Does the bagged stuff bruise easier? I noticed in some shops the grocery staff can be pretty rough with the produce. Maybe the clamshell keeps the spinach fresher longer because it prevents it being squeezed/bashed about?
Is one pre-washed and the other not?