The pricing and payment conditions will be announced when the EF19 web sites goes online (or shortly afterwards), we still have to clarify some details. Start of registration is scheduled for January, 19th.
Last year, you had to pay the convention fee and stage ticket within two weeks after confirmation of the registration and the remaining amount (hotel room) until March, 30th. I don't know if it is going to be the same this year, though.
(BTW, you can upgrade to Sponsor and Super Sponsor at any time, but we may run out of goodies if you are doing so after we've ordered them...)
Eurofurence does not give any refunds, but in you may sell your membership if you cannot attend. However, this requires approval by the registration manager as the attendance is bound to the person (i.e., you cannot just show up with the registration for a different person.) Please do not expect anyone purchasing your registration without a paid hotel room at the Maritim, though.
Anyway, the details will be announced shortly before registration starts later this month.