In most large organizations, each level of management has a pre-set spending limit. For example, a supervisor can approve $3,000, a manger $10,000, a Director $100,000, a VP $250,000, etc. Depending on the size of your purchase, you have to go higher up the chain to justify it. Most engineers don't have signing authority to actually buy anything.
As for refurb equipment.. Generally, it's not looked upon as a good source of hardware, unless the budget is really tight or there are mitigating circumstances. Refurb equipment has one major advantage - Availability. If you CAN buy it refurb, it's in stock and can get shipped quickly. It's not like distributors who try to minimize their inventory and end up waiting for the manufacturer to build something.
I've only used refurb gear extensively in one case - At my previous job, we had a company-wide Sun maintenance contract. It covered everything Sun no matter how it was purchased. Sun doesn't change their servers that often, so we could buy current model servers that were refurbs and fully covered under our service contract. We saved about 30% and got the same service as a new box.
In general, however, I always recommend that people NOT buy refurb gear, unless it's the last possibility, for budget or availability. You don't know what that server has gone through - Was it used by a grandma to browse church.com every sunday or was it used as a massive database engine that was hammered all day long?
Looks like you've got some interesting answers, hope we've helped!
- G