Do they sell unlimited tickets at that price, or is like Megabus where the first person might get a $1 ticket but the price goes up as more are sold? There's p

Do they sell unlimited tickets at that price, or is like Megabus where the first person might get a $1 ticket but the price goes up as more are sold? There's probably a lot of business in people checking Ryanair's website thinking "Maybe I can get a £9 ticket" and ending up with "£65 is still pretty good."