You do not need to re-upload Grasshopper files every time your Google Sheet data is modified, but you do have to pay attention to the caching system, as I mentioned in this topic previously.
After updating a Google Sheet, you will either need to clear the cache of your models or to use a random seed parameter to make sure the solution returned by ShapeDiver is not already cached by the system.
Note that this would not be necessary if you would upload a new Excel file to be referenced in your models instead of using the Google Sheet solution. But in any case, one or the other per-model update is needed, although it is less cumbersome than re-uploading ShapeDiver models from scratch.
A completely automatic way to handle this pricing update workflow would be to embed the models in a website and implement a mechanism relying on timestamps (for example), which would make sure the solutions returned by ShapeDiver are never cached.