I guess the whole point is.. it depends.
Over here for example, you simply do not find yoghurt drop, it's not a common product (and importing them is not cost effective with the transport).
For mealies, breeding them is inexpensive, qnd when sold around 3.5€ the 50gr, it is a lot cheaper to breed them (without considering the hassle it can be to go fetch fresh ones when you do not have a petshop nearby, and that you have several animals eating them).
It can also be safer, since you do not know with what mealworms you buy have been fed (nor how many fillers have been food in commercial yoghurt drops)