After posting on this thread earlier today, I sent an e-mail to Spirit Airlines complaining about this new pricing policy. I explained that I was a loyal Spirit customer, but they are forcing me to book with other airlines. The Spirit price for my days in January for three people is over $2100. I paid $513 on Airtran non-stop with great times. You'd have to be crazy.
I don't know if they will respond, but I'll post if I hear anything from them.