I'm searching for flights mid-April with a mid-May (dates are flexible) and I can't find a non-stop flight between either airport in Taipei and Shanghai for less than about $800 per person on a non-chinese carrier. I've check ctrip, travelzen, and expedia.

What gives? I know this is a regulated route, but that's a bit much IMO. For my flight before chinese new year, I could get a roundtrip for about $400 on TransAsia. Do fares tend to drop closer to the travel dates or is there some event happening in either city I'm not aware of in April/May.