These OLCI prices seem quite good, for both Y to W and Y to J.
I for one would never take a Premium Eco upgrade because the seats shape make it impossible to sleep in but depending on your flight time/sleeping habits, this might not be a problem to you. Business is definitely another world from Eco.

You can expect prices to increase at the airport. I never had a better deal at the front desk than online. Usually it was 20%-50% more expensive at the airport, but of course that's not a rule, just a personal experience.