Meidel,
I've got used to the 14x12 tho only 5' myself.
I got used to them a decade ago - by choice. The frames need to be lifted about 320mm for TBS or slightly less if BBS. Yes, they are heavier than a deep frame but that is not particularly height correlated (more 'arm length' and strength). They also need to be lifted beyond the box for inspection. One can adjust the hive stand to suit your best working height, surely, so no real prolem apart from the extra weight, as I see it.
Shifting a full box is far heavier than a deep, however. I would not recommend to demaree with a 14 x 12.
But I think 16x10 equipment are cheaper than the 14x12 frames and foundation. So there's that to consider as well.
I have bought sales seconds and gone the way of buying deeps and adding my own eke. I have always found that frames are available at good rates - a little over 80p a throw in the sales (cheap enough for me to have never set about making them myself).
Commercial boxes (and frames?) do not seem to be offered at such competitive rates, if they appear in the sales at all.
Foundation is neither here nor there, pricewise.
So I reckon the 14 x 12 route is considerably cheaper than the commercial option.
I like the deeper frames as the brood nest can be more circular in cross section and leave a honey arch. Just my choices, but I would like to see jusification of your claim of commercials being cheaper.
RAB