Don't put limits on who we can purchase from. You give us this tiny list with a few vendors. They can charge us outrageous sums for stuff I could get for 70% less on Amazon or some other online retailer or even at my own onsite retail store.
In my service, I needed to buy HDMI cables for 12 TVs... they were almost 20.00 apiece. Amazon was having a sale for same quality and length cords for .98 plus 3.98 S&H. I could have saved 15x12=180.00 bucks... but I had to use special vendors. (When I got home I bought some for myself... they've worked fine for a year and a half.)
Small example on my part... but I imagine that adds up for each employee over time.