As a regular person, you get miles for flying when you fly (if you are in the airline's frequent flyer program) and miles for paying when you pay (if you use a mileage-earning credit card).
However, a "regular person" does not buy 31 tickets. Airlines have a variety of programs to compensate people who do. Some of those programs are designed for small businesses. ("Small" means "too small to negotiate a corporate discount.") The business account receives credit for all tickets that employees buy and/or fly, depending on the specifics of the program. That credit can then be used for the same sorts of rewards that you can get with miles, sometimes including status for one or more designated employees. For example, with American Airlines' Business Extra program, you earn one point for every $5 you spend on tickets. Free flights start at 2,000 points, and Gold status costs 3,200 points. I don't know about Southwest, but they probably have something comparable. If you don't have a small business you can sign up for this program, you may have to invent one. "Pookynubbers' Lemonade Stand" will do nicely, or "Pookynubbers Management Consultants" if you want to sound more impressive.
You can also call the airline's group sales desk (you'll have to if you want to get more than 9 seats on the same flight in one transaction; the reasons relate to how they manage access to their database and would be off-topic here) and find out what sort of discount you'll get for 31. That's basically what beckoa suggested above. The savings may be worth more than what you can get any other way.