The GE prices as shown on the website and via the public API calls (used in spreadsheets, etc) are not in sync to the in game GE. For an example look at clean toadflax. On Nov 27th it stopped updating, did one on Dec 4th, and it hasn't updated again since. This is blatantly visible on the price graph if you look at the dates on the "dots".
It did this once before and it was out for weeks. Interestingly enough the Runescape Wiki does have valid prices, or at least more so than the website. Which is weird because I looked at their bot code to retrieve it and it's using the same API call my spreadsheet does. I need to dig through it again and see if it's using the same server.
But I bet it is, and they are giving them special treatment. Which is fine but what about the main website here?