What’s the best way to get from Tokyo to Kyoto without spending a fortune?

I'm looking for the most economical way to get from Tokyo to Kyoto for the first time (haven't done much outside of Tokyo and always wanted to visit Kyoto).

The Shinkansen is the most convenient but the current prices are crazy. Has anyone here ever taken night buses, airlines, or other train services? Would you mind sharing costs and your general experience? Comfort is not a priority.