I went to the Southwest website and if you go through the links it just takes you to the Disney website. You always save money by advance purchasing tickets as opposed to buying them at the gate. It is sometimes difficult to advance purchase discounted regular PH passes (without the pluses) at many of the online ticket brokers, however, you can easily advance purchase PHP passes and we have found it is often cheaper to go to these brokers (you may also want to check out
AAA if you are a member) We have used ticketmania.com, discountorlandovacation.com and officialticketcenter.com and have had a good experience with all of them. As an example, here are the comparative prices on an adult 7-day PHP:
ticketmania = $330
officialticketcenter = $317
discountorlando = $325
Disney website = $336.54
One additional thing that you need to consider is shipping. Ticketmania will deliver to your hotel for free, so the tickets will be there when you check in. Officialticketcenter charges $5 for hotel delivery or you can pick up your tickets at their office (very close to WDW) and avoid the charge. Discountorlando requires Fedex delivery at a cost of $10 or you can pick up the tickets at their offices and avoid the charge. We've never ordered from Disney, so I'm not certain about their shipping policy.
Hope this helps!