I doubt that the introduction of 4k clips would result in a price increase, but it would cause the cost to Totem to increase. Any introduction of a new resolution implies extra post-production effort, extra QA effort (the QA team are volunteers so their time is nominally free but it would still slow down the QA process and entail extra effort by Totem themselves). Also extra server storage space would be needed - the storage on the server would almost triple - and extra network capacity would be required. As the proportion of users that would benefit from 4k cards is likely to be small I think it quite understandable if Totem do not think that providing 4k clips is worth their while at the moment.