When is buying fruit for making preserves the frugal thing?

There are two kinds of jam that I think is frugal to make. 1) jam with any kind of free fruit. This would include fruit from our bushes and trees, foraged fruit, and any fresh fruit that is going soft and I would enjoy in jam. 2) The second kind of jam that I like to make does use purchased fruit. However, it is frugal if the only commercial versions of this flavor of jam are an expensive brand, such as cherry preserves or blueberry jam. Both of those flavors are only available in "gourmet" brands of jam, in my area.

A week ago I posted a photo of some Bonne Maman preserves jars.
This is a très expensive brand of jam. For some flavors, this is the only brand available in regular supermarkets.

I love blueberry jam. The 13-oz jars of Bonne Maman Blueberry Preserves are $4.99 at Fred Meyer or $4.69 at WinCo.

By making my own blueberry jam with purchased, fresh blueberries, I can make about 3 of those jars-worth of blueberry preserves for about $3.80, including berries, sugar, lemon juice, pectin, and new lids for the previously-used jars, for almost one-quarter of the cost. That's $1.27 for 13 ounces of homemade blueberry preserves. I use several sizes of jars in one batch, so some jars can be for our consumption, while others make perfect gifts.

   

While it may not be very frugal to make many types of jam with purchased fruit, it can be frugal to buy fruit to make specialty preserves. And, well, sometimes I'm just a "specialty" kind of gal. (Not that I'm high maintenance! ha ha)