The idea is such that for the online part, i.e. the ability to see and interact with other people's creations in the game, the initial price will cover the associated costs of bandwidth and server processor time for some period, say half of year or so. The period can be then extended for a price, but I expect the price to include only the costs of cloud transactions one will consume so that we aren't losing on it. We don't have the calculations yet, it will become clear after initial tests.
For offline gaming no additional payments will be necessary. Note offline here refers to being offline from the global server, a lone man on the planet. Technically, multiplayer sub-games with custom servers could be used in both the online and offline mode, though I don't know yet how of if it could be combined.