I use fairly high end hardware, but only buy devices, or batteries for them, infrequently. Good devices really do stand up better than the mass produced ones, are cheaper in the long term. I vape 6 ml/day, but got into DIY after only a few months.
I haven't bothered with an RBA yet, tend to use pricey but very good cartos, and pretty good atties.
Early on, stock KR808D-1, then Riva/eGo gear, vendor eliquid at 3 ml/day, I ran about $4.25/day all-in (including S&H). Since switching to good VV PVs, and DIY at 6 ml/day, my running cost has been about $2 - $2.25/day. As a PAD smoker, cigs were running over $9/day where I live, so I was saving even the first couple months.