f/1.4 new is about $5xx IIRC.
The only difference I see is that half-stop of light, and the extra weight, definitely not worth the $ IYAM.
There is difference in that half-stop of light and the DOF, but frankly, to my newbie eyes, I can't discern the difference, and not too much difference in image quality against the f/1.8.
Soft at f/1.4 wide open however, but stepped up already gives good image quality.
$5xx