from a juice diy-er's point of view:
yes, making your own juice is a lot cheaper than buying commercial ones.
also, you claim you are too busy with work to make your own juice? funny you would say that because mixing your own e-juice would take just a few minutes, and if you make more than 100 ml per batch, you're making juice good for several days at the least.
personally, i mix "test juice" at around 5-10 ml, just to taste it up, and if i like it, next is making anywhere between 30 to 200 ml at a time.