I'm a bit confused here. The idea of a flavoring that is not known to make great juice is less expensive how? I know Capella's Sweet Tangerine at 15% makes a great juice and costs about $6 for 13ml which makes over 80ml of juice. How much cheap flavoring do I have to buy and experiment with to make a great vape? I don't know, but it's a very short path to hitting the $6 mark which makes the cheap stuff more expensive real quick.
When I started I questioned everything. I tried flavorings that nobody was using, from all kinds of sources. As an example, I tried these big bottles of baking extractions. They were cheap and smelled great. They busted a number of dripping/test attys and never could get them to make a half way workable juice. I considered them an expensive way to get some great bottles to premix my PG and VG together after all was said and done. I don't discourage anyone else from trying these kinds of things, but to think it is a less expensive way to go is completely wrong. I never thought it was going to be cheap doing what others weren't and it wasn't. I did discover some stuff, but you have to pay for education when going your own way. For folks that want a cheap and easy way to make their own juice I nearly always recommend Cap's Sweet Tangerine at 15% because it just works and anybody can do it.
Oils, yes I use some. Mostly mint oils. There are risks with a type of pneumonia from inhaling veggy and mineral oil. Mint oils have not been linked to this risk as far as I know. (Look up the health risks of the demographic of fire-eaters and you will find this lung issue from inhaling oils being fairly common.) And to further confuse the issue is that Lorann's Oils is a trademarked brand name and a majority of their flavorings are not actually oils. But if anyone wants mint flavor and wants to avoid oils there is TPA/TFA who has mint flavorings that are PG based. While it takes much more PG based mint flavoring to have the same taste impact than mint oils, it's still a good way to go. When I choose to avoid oils, it is because they can be an absolute bear to mix. (I abandoned one recipe that required the bottles to be placed on a homemade vibrator for a week to get the oil to mix because the noise drove everyone in the house nuts.) Oddly enough I am currently vaping a juice that has a tiny touch of anise oil which makes it just perfect and the tiny amount mixes just fine. I don't recommend using oils, more so because they are tough to work with than the risks, but I do note that mint oils can be used in tiny amounts.
Gums, sugars and fats will clog heating coils. These are common in flavorings used in baking. Even natural vanilla flavoring will have fats and sugars to add to the fact that it is weak and will require a higher percentage of flavoring makes it undesirable. I vaguely remember a few years ago someone posted they got a McCorm's flavoring to work for them somewhere around 50% total flavoring. Since that brand is generally considered weak, that fits fairly well, but I've since tired of working with weak flavorings so I have never attempted working with them.
There are a number of reasons that you find nearly everyone here using PG and alcohol based flavorings, and a few VG based, and not looking at $/ml of flavoring. The value conscious are looking at $/cubic yards of great vape or $/fun time.
I encourage you to try the flavorings from your local store. Experiment and report back. Feel free to use my flavoring level blog as a guide in your experiments if you like. If you were to track all your costs to make a good vape with these flavorings and report that too, I think you would be providing a great service to other mixers. That's the best part of this sub, the experimenting.