Your description of the work environment sounds great, and it's awesome you recognize and appreciate that. High pay comes with high stress, high responsibility, and worse working conditions. Lower pay comes with less stress, and better working conditions. You have that -- be happy!
Your employer can't pay for you to go to the conference. That they offered to pay for the training (if you get yourself there) is better than zero! Some would call it half-assed but it's all about that glass with water and how you see it.
Treat it as a vacation to Las Vegas (one of the cheaper places to visit) and during that vacation... IF YOU SO CHOOSE you can attend a seminar/conference that your employer is willing to pay for. If you don't, it's a vacation.
Hotels are inexpensive both on and off The Strip. Rental cars are unnecessary but $20/day (seriously). Food is plentiful and cheap so long as you walk through a casino to get to it. Drinks are free while gaming. There are shows all over the place.
If it was my job and I really wanted to attend this conference I'd book a reasonable hotel (I love Mandalay Bay or MGM or Planet Hollywood) close to the conference, get a flight in on a cheap air carrier (American formerly AmericaWest and SouthWest and JetBlue are three popular options), take a $9 shuttle or $20 cab from the airport, and party my little ass off until conference time. I would get myself tickets to see a show or two while out there.
Instead of begging for $$$s, ask who wants to come with and make it into a party-atmosphere for a small group. Well worth digging into the credit-card for the once-in-a-decade experience. Have a bachelor's party/bachelorette party atmosphere without the wedding. Skip the limo :)
Enjoy the trip. Enjoy the show!
Full disclosure: I go to Vegas about 4 times a year.