....and he replies to his own posts into the bargain

:lol:

Seriously, it is an old-fashioned saying that isn't used much anymore.

Like CRIKEY which was resurrected by the croc hunter Steve Erwin.

It means "as well as" or "on top of that."

Comes from the old days of bartering when one or both sides would ask for something extra to seal the deal.

"On top of the bargain I'll throw in a roadworthy certificate"

"on top of the bagain he's running in the Caulfield Cup the Cox Plate and the Melbourne Cup!"

One great racecaller who uses old turns of phrase and I love to listen to him is Jack Styrling (I think it's spelled right???).
He rarely calls but when he does it really takes you back to the early days.