fearlessbaker, this is a public forum and everyone is entitled to post their opinion, just a you shared yours.
I remember her talking about her Grandmother's house. Also, I have about five boxes of cake mix in my bakery. They whip up in a few minutes and provide the perfect "dummy" for practicing a new fondant or buttercream technique. Right now I have a monsterous bucket of But-R-Cream (fake from Sam's) in my bakery. The junior class left it there when they made cupcakes for their bake sale. I couldn't get anyone to take it home. Now I'm trying to give it away.
One note on quality. If you do use all off brand products, the quality is affected, especially in taste. They may not sell well against a cake made with name brand products at the same price. On the other hand, if you want to sell a scratch cake at the lowest price, this may work. Just make sure the cake is better than a box mix. Scratch made cheaply may not be as good as the box mix, making the box a better option for the market.
And by the way, I got stopped at Sam's loading that bucket of fake buttercream in my SUV. The two well dressed ladies were asking about my business because of the wrap on the back of the vehicle. I had to explain that the big bucket was for a school project, not my bakery.