The point is, that the only way to (legally) aquire magsafe connectors is to cut them off Apple's power supplies. The MagSafe connector includes a "DRM" chip, which does the handshake with the MacBook and there are no third parties selling "pirated" MagSafe connectors.
As for the batteries, yes, I expect there'll be people who figure out how to replace the batteries without replacing the top-case + keyboard + trackpad in a package for $50-$150, but in many cases it'll be a worse value than getting a new, shiny top-case + keyboard + trackpad as a part of Apple's $200 battery deal. Damaged top-case components are fairly common in second-hand 'Books and replacing those will probably get a better re-sale value than just replacing the battery or selling with a damaged battery + worn top-case parts.