The g935 is a curved screen; No, it will not fit a g930 phone... That's like pushing a square peg through a circular hole .. Like why won't a bike tire fit my car? They are both tires, right?
... Just expect every model of phone to have it's own screen and none of them are compatible with each other. There are exceptions to the rule, of course, but you will save yourself some grief if you accept the fact.
Are you looking for parts or a repair? Are you only looking in the one place if it's for parts? If you check with a number of different suppliers, the prices will vary. In my experience the g930 is the less expensive of the two models to repair so the prices you have been given are strange to me.