Thanks but it's not likely that I will buy the additional three units I need from Apple.
I use the MBP in four different locations. It is moved between these locations daily. If this doesn't wear out any single adapter, then I don't know what will. Plugging, unplugging, wrapping and schlepping every trip is just the thing to assure a left-at-home adapter when I need it most. The strategy is for power at all locations. It has worked for all my iBooks for ten years when third party units could be counted on. The transformers aren't the problem. It's the connectors and the sub-par make of the flexing parts.
I need at least three additional units to leave on site at the remote locations. That's one heck of a good reason to own less expensive adapters. So, for me, this question remains unanswered.
$320. for three additional new OEM units, added to the cost of the used MacBook Pro I just bought, pushes the whole deal to the limits.
(Just one look at the 1.3 star rating on the product image you sent tells me that the factory units are not a good buy if they are actually used daily.)
If Apple (who makes amazingly good quality products) continues to make every item only Apple-replaceable, then the parts should be of the same quality as the other hardware, not the quality of GM's ignition switches.
Used pre-owned OEM units seem to be the best deal if carefully selected.
--GG