Hello and welcome to the site,
The quality of the SS Weber grate is very nice but the upcharge is a bit frustrating IMO considering the $70 is above and beyond the cost of the standard grate. There are also other quality stainless steel grate options out there (like the hunsaker etc) but many of the alternate choices do not include the circular center cutout (GBS system) made to accomodate Weber accessories like the wok, dutch oven, griddles etc.
If you currently have GBS components that will drop in then its probably worth it as the grate will also last significantly longer than the plated version... if you dont already have the GBS accessories, or plan to get some, then just stick with a quality SS hinged grate.