"My last 5-day cross-country business trip cost $1100 and I stayed at a pretty decent hotel."
Sorry, but I don't believe it. We're talking conference travel here, not a business trip. I'm on the speaker's circuit and travel to up to 12 conferences a year, plus incidental personal travel. Some conferences charge as much as $900 for registration fees. The cheapest conference I went to last year charged $300. There was one occasion with back to back conferences over 6 day period and the registration alone was $1450. It isn't cheap to rent out a conference center. For a national or international meeting the cost can easily go over a quarter million.
And yes, my last business trip was $1100 and some change. But I was looking at aircraft parts and machining processes, not attending a conference. And the flight between Salt Lake and Cleveland was only about $380, which is pretty low. Most of the 3- or 4-day trips I take are right around $900-$1000, so maybe my company just has a really good contract with the airline. And I'm usually looking at facilties, aircraft parts, and machining processes so there's no conference fees or costs like that.