I absolutely understand your confusion; as often happens w/department stores, the names of the TOD'S bags in the photos are stated incorrectly. The photos both appear to depict the G-bag Sacca Grande. The Saks description, however, states the dimensions of the bag as 20"W X 11½"H X 11"D. Based on these dimensions, I would assume this is the description of the G-bag Shopping Grande (photo below), not the Sacca Grande.
The NM site lists the name as G-bag media tote, which is a totally different bag altogether. It is the bag depicted here:
http://www.saksfifthavenue.com/main...282574492708980&bmUID=1250710593560&ev19=1:28
In my experience, NM & Saks often tie the price to the name of the bag, so the prices listed might be for the bag names listed, not the bags depicted in the photos. I have definitely seen this happen in the past.
At the boutiques, I believe the price for the G-bag Sacca Grande (also known as Provence) is somewhere in the neighborhood of $825.00. And I think it's about $765.00 in the media size. Hope this helps. Please don't hesitate to ask additional questions if we can help clarify anything at all. The folks on tPF have been so helpful to me as I've been learning about TOD'S, and I'm more than happy to pass this along.