I both DIY, and buy commercial. I have about 800ml/base, enough nic for twice that, and enough flavorings for much more. Plus I have about 800ml of commercial in various strengths, also refrigerated. I give a lot of juice to my employees though. I'll vape ~15 different flavors in a day, love the variety. Buying the commercial stuff gives me lots of DIY ideas, but I don't think I'll buy any more DIY stuff. Buying good commercial in quantity is getting cheaper and DIY isn't as fun, or satisfying, as I had hoped. I buy my commercial from AIV and from Ahlusion, and especially with Ahlusion, just can't DIY juice as good as that.
I agree with you 100% on the brew that the commercial folks come up with...especially if we like a variety of flavors. Its pretty hard to compete with unless brewing was my main job.