Their pricing is strange, but it is also cheap.

I have noticed that sometimes the low fares are only one way, so one side of a round trip costs more, raising the total price, then of course are the fees.

These Tuesday Wednesday Fares sort of do the same thing. Who really would fly somewhere on Tuesday and return Wednesday? Its too early in the week for a Weekend getaway, so I suspect usually they sold one $15 fare and one at a higher price.

I have a half fast theory that Frontier has now completed all or most of the changes they intend to make to become a ULCC. They inflicted the pain on their existing customers all at once instead of stringing out the changes and the are now making a move in the market to establish themselves as a really really cheap airline.

I wonder if the strategy is to slowly back off these very low fares once they have established their reputation.

I find Spirit is now often not the lowest fare. Southwest continues to talk low fares but they are often not the lowest, even when you take actual bag fees into account. Yet many people believe one or the other is always cheapest.