I think sometimes it comes down to whether you are a hobbyist or a professional producing one cake on a semi-regular basis (hobbyist) or multiple cakes a week (pro). I am a hobbyist and buying fondant is expensive. I cannot get the larger tubs around my neck of the woods so they have to be ordered. Factor in postage and
wow, this becomes an expensive hobby! I make quality fondant for very little money and can, therefore, maintain my creativity while being cost conscience. I realize for professional bakers, the Economics term, "Opportunity Cost" comes into play for them. It is a time saver to open a tub of premade fondant vs. the time it takes to make it in quantity. Time is money when they are factoring the total cost of their cakes.