I fly on Low Cost Carriers in Europe such as Vuelling and I am used to looking over their policies before I book. This coming May my Folks and I are flying to Cancun on Volaris from Oakland for $495 r/t with checked luggage and carryon included plus personal item. I always choose the highest package available because I understand the unbundeling that LCCa do.
As for arriving at the airport I always allow for 3 hours especially on LCC and check-in online. I think the $50 you paid is reasonable because on other airlines you would have had to buy a new ticket.
Next time you will know to not cut the airline cutoff by 2 minutes. I research the cut off times in advance.
United wanted $700 and not including checked bags.