Everywhere I've ever worked has had a standard policy of buying non-refundable tickets whenever feasible. I've worked for several companies large and small, some with lots of client-billable travel and some with little. All have followed the same logic: even if you have to change or throw one away every now and then, the company still comes out ahead by buying most tickets as non-refundable.

I've been lucky in that most places I've worked have provided only "general guidance" in most areas of travel, allowing the traveler to use good judgment. For example, I've never been locked into a hotel or rental car program I didn't like. Or an airline I didn't like. But part of that common sense is to try, whenever you can, to get decent airfare.

At my current company, everybody up to the top buys Y. We even fly a lot of Southwest since a couple of our popular routes are on their nonstops. (Those tickets also have the side benefit of being changeable, somewhat reducing the distinction of whether or not the ticket was nonrefundable.)