The Red and Blue lines were built cheaply, the City in the past proudly pointed out how economical they were. And they were successful from the start because they ran through existing transit corridors of good ridership. And even then there was significant pauses in the expansion of the Red Line and the West LRT opened 27 years after the NE.
The problem I see is that the Green Line got so much money because it was supposed to pay for the primary network, from Panorama Hills to Seton. With one project, the two main transit priorities in Calgary (replacing the overcrowded buses in NC Calgary, improving service to the growing deep SE) could be addressed. Effectively, an entire generation of of transit capital funding was assembled for this purpose. Calgary will have to wait its turn for more from higher levels of government as well as figure out where to get more money from its own resources. The City of Calgary's capital and financing spending for Stage 1 ties up $75M/year of property taxes for the next 30 years, and will have to find new funding to pay for the operating costs of Stage 1 And the cost of expansion is steep, going to Panorama Hills or even 96th by itself will be the second most expensive infrastructure project in Calgary history.