You can use
pcbshopper.com to compare prices between many fab houses, but
EasyEDA usually is the cheapest alternative anyway.
I've used it a couple of times and have been impressed by the quality of their PCBs.
The usual route is to use their free, web-based tools to do the schematic capture, any simulation required and the PCB layout and then generate the Gerbers (which are free to download and can be used with any PCB fab house: there's no tie to EasyEDA). From within EasyEDA, the Gerbers can be submitted straight to EasyEDA for fab.
However, it is equally possible to submit 3rd party Gerbers to EasyEDA for fab. It is also possible to import existing designs done in Altium, Eagle and KiCad and edit them in EasyEDA prior to PCB Gerber generation.
Their pricing and design rules are here:
https://easyeda.com/Doc/Tutorial/PCBOrder.htm