On the front of using a much cheaper display module, just got Ucglib running on Arduino for ESP:
If interested to give it a try, my port is at https://github.com/spapadim/ucglib (let me know if it worked). It also requires two simple patches to the Arduino ESP install: https://gist.github.com/spapadim/a4bc258df47f00831006. I believe that u8glib could also be ported in a similar fashion (but not interested in doing it right now).
Support for the touchscreen controller is still missing (shouldn't be hard, though).
Note: there is also a port of ucglib to NodeMCU at https://github.com/devsaurus/nodemcu-firmware/tree/dev-ucglib (which convinced me to give the Arduino port a try; thanks!!). That port strips out most fonts from the source (avoiding this was the part that took me a while to get working).