With the price of PG, VG and flavoring I fail to understand why the big web players and the local shops are selling it at such a high price. The small shops with low sales volume an higher price may be understandable but not for the high volume web sites.
I tried some of the cheaper chinese products and did not see a difference with others. Unkonwn or Inadequate quality control keeps me away from those.
I have started to make my own as the end price is on average about 10 times less.

I would certainly quit making my own if I could pay a fair price for commercial e-liquids. 2 to 3 times my cost but no more. I guess it is a matter of principle as much as economical
When I was buying juice I was generally paying about $0.30 a ml. Now that I make my own it's considerable less, though living in Canada it's at least a couple of times more than you are able to make it for. If we were making it in large quantities it would be cheaper too.
However, as Susan~S said, it's more complex than that.
I haven't done any research on this and I haven't run any numbers as I'm not interested in making and selling juice. However a few things come to mind.
Even a small home based shop needs a very clean space for this business. You can't be making juice in a room of your house that the dog walked through yesterday. You need clean, safe space to store your supplies in, concentrated nic base needs to be safely stored and handled in a ventilated space with adequate safety measures taken for the people who are working with it, clean containers and mixing and measuring gear, nic testing supplies, labeling equipment and packing. A system for making sure your orders are filled and shipped accurately. Bookkeeping has to be done and business income tax has to be taken care of. You need a lawyer. Someone has to answer the phone and email when people ask you questions. You also need knowledge of what is safe and know best practices for doing this job. Plus you need recipes for juices that people want to buy.
You should have liability insurance which isn't cheap, or you will be on your own if someone sues you. You'll need a commercial website. And to run all this you'll need to put in your own time or pay someone else to do that. How much (or how little) are you willing to pay yourself per hour?
If you can't work from home you'll need to rent a commercial unit.
I know there is money in this, but it's not as easy as it may look at first glance
