Well, that depends on many factors. First, you need to consider that Southwest is one of the companies that has moved to a revenue-based system of miles accrual, so a point is likely to have different value depending on your class: Wanna Get Away, Anytime or Business Select. The higher the class, the cheaper the point. On points earning, the relation is negative: more expensive fares will gain you up to twice points more.
So basically, if you want to book here and now and don’t care for your future mileage balance, book Wanna Get Away. Southwest is an airline that specializes in domestic travels, so these are the cheapest and most profitable. As for international, you won’t find a lot of them, but Southwest does fly to Mexico, Canada, Costa Rica and some more.
Southwest is quite liberal in terms of letting you know the fares. You may easily find the well working search engine on the site that allows you to search see available flights on points or a fare map. All of that without even logging in! Generally, domestic Wanna Get Away flights cost around 9k point, Anytime around 20k and Business select around 30k. International flights are roughly 20k Wanna Get Away, 40k Anytime and 50k Business Select.
Speaking of earning the points, when flying Wanna Get Away class you earn 6 points per flight, 10 for Anytime and 12 for Business select. You can earn even more if you add a co-branded credit card like one of the Southwest credit cards or a general travel credit card like Discover it® Miles. Don’t forget to register in the Southwest frequent flyer program Rapid Rewards that will actually allow you to earn and redeem the points.