First, I have not found that Joanns has less expensive material- on the contrary, I can always find a better buy elsewhere.
Second, you put a lot of work in sewing an item, so using high quality material makes sense. The only exception is when I make a proto-type in order to experiment and come up with a pattern. I once cut up and used worn-out stuff sacks to test a backpack design.
Internet buying frustrates me because they charge an arm and leg for "shipping and handling" for outdoor material, which really ships cheaply because it is light weight. Often you will pay more for shipping than the material!