Future energy ecosystems need new market structures and interactions between TSO and DSOs, in order to realise distributed ancillary services. This paper estimates and compares ICT costs of several TSO-DSO coordination and market engagements proposed in the SmartNet project. A hybrid cost estimation methodology, which utilises constructive cost model methodology, expert estimates, a national DSO regulation model, and implementation of a simulator, is employed to estimate the development costs of aggregation and market clearing systems needed to realise the market schemes. ICT costs of different arrangements turn out to be at the same level and they are minor in comparison to energy-related costs. However, depending on the overall design of the markets for distributed flexibility, aggregators may have the largest ICT costs and investment needs.