Not sure what the situation is in the US, but in Australia you can't book direct with Globus. In Australia, there is no discounting - the brochure price is what you pay through any agent. I would imagine though if there is any discounting it would be the travel agents who could obtain it.
It is worth knowing that you get discounts if you book and pay well in advance. These are fixed discounts, of 2.5%. . Can't recall exactly how far in advance you had to book, but 2-3 months at least.

You can book with AffordableTours.com -- They have great service and will give you a big discount on your tour (up to 14%). .