I've called Southwest on this before and they told me that the reason the price was higher was because they only had so many tickets at the lower price. I'm curious if this is really true. Did you get 3 at a lower price and then 2 at a higher price? Airlines make me crazy with their games!
I only had around 90,000 points to use so I played around with the passenger number to see how many tickets I could get with that amount. It did seem to me that the more people I added the more the point amounts went up. We are flying out on Saturday and back on Friday so I knew those days would greatly affect the points needed.
I booked my two paid for tickets one at a time since I had the vouchers. Even those two tickets booked right after each other were different in price by $ 10-15.
It is a total guessing game to me on when is the best time to book. I just watch and see a fare I feel comfortable with and book it then hope for a reduction later.
Hope this helps and you get what you need!
My suspicion is it will be available again at some point. I feel pretty strong about this, as I watch daily and have seen it happen. I think they want people to book/fill the other flights.