ASFKAP - I would very much doubt you'll be seeing sales for 1 cent / 1 penny, except on the most abysmally performing routes in the lowest of seasons.
There's too many people out there with a prepaid Mastercard who when they see a 1 cent sale, will just buy up seats on lots of dates, on the expectation that they will fly very few of them indeed. If you buy up a seat on 1,000 different flights, the total price is 10 euros - the only real cost is the time reentering your details on the website. If you don't expect to use a flight,you are most unlikelyto book a hotel or bus transfer through FR's website.
If you don't take the flight, FR thus end up with zero ancillary revenue. If you do show up, FR still have to pay airport fees and any kind of Govt tax - unlikely to be covered by the profits on selling a sandwich + coffee on the flight.
IMHO, the only benefit to Ryanair of a 1 cent sale would be as a marketing tool (bait and switch) to drum up demand at the very lowest of seasons, e.g. mid November
Selling seats for at least 5 euros means that even with a prepaid Mastercard, it becomes much less likely that a single person will buy up dozens of tickets without expecting to use them. I suspect also that if someone genuinely wants a ticket for a flight, 5 euros will be low enough to grab their interest