Early in a project you want experienced people putting in lots of time (full time) on architecture and initial design and MVP. Later on, lower paid programmers can evolve the project part time to add javascript flavor of the month.
As an alternative financial model, how about 25KE (or more) for two months for expert level programmers to bootstrap a new project full time only, or 60KE for a year to evolve features and squash bugs on an existing project perhaps part time. Or if politics and PR make ongoing support impossible, then only do the bootstrap phase.
Its possible programmer salaries in .de are much lower than I think they are. However they can't too much lower, someone there is buying all those BMWs and VWs.