Just in case you are just needing a suggestion for what to include in a letter you write to justify your trip within your office, they have a sample letter on the bottom of this page
Esri UC | Why Attend
edit: I just looked at the letter and, although maybe obvious, the Hotel and Meals estimated at the bottom are per night/day. Of course that all varies as to where you stay and what you eat. There are tips and tricks from previous years on geonet to help keep some of these costs down (i.e. staying further our and taking the trolley (or UBER/LYFT) and taking advantage of the evening socials where appetizers are served, etc).
Here's a proposal letter you can customize and a one-sheeter you can download to justify your trip.