I wouldn't stress too much; 480 is pretty standard on that route (and, I've paid as low as 220 in the past). The only risk is that there aren't nearly as many flights to PVG as there are SHA (around 7 v. around 40). As a fallback, you could always fly down the day before, in which case, SHA would be a better option. Nevertheless, I will PM you when I get back there (not sure when that will be exactly, but sometime within the next 2 or 3 weeks).