The price is right. Corporations buy from Graingers, MSC, McMaster Carr, and similar. As posted above, they usually have discounts negotiated and payment terms that benefit the corporation. They all ship immediately, and have several distribution centers so usually you get the item the next day, even with standard ground shipping. They also carry a large inventory so you almost never come across a backordered item. For this level of service, the price is a premium.
I work for a corporation and we buy from MSC on a daily basis. Its in our system, and the corporation approval process is in place. I can get a Dewalt Drill for 300 from MSC, or the same model for 180 from Home Depot. I get it from MSC because thats the way my company is set up to do business.
If my company wanted a pool table, buying from one of these companies offering it for sale that we are already set up to do business with is going to be much easier than getting it from a local pool hall for 3000. Thats just life in the corporate world.