The idea here is to expand the formula editor (Specifically CASE WHEN Statements) to allow the creation of dimensions or "buckets" based on filtered data. This is useful on the dashboard level as we ...
Workarounds for this:
For the pie chart, don't put anything on categories and instead create a value per bucket.
e.g. IF ( [Avg Money Spent] > 999 , 1 , 0 ) and rename the value to "1000+" etc.
And for a filter, say a Pivot with customer details on rows and values for spend, put a widget filter on the customer ID, Ranking type, TOP 100000 with a formula like IF ( [Avg Money Spent] > 999 , 1 , NULL ), where NULL will exclude non-qualified customers from being included in the ranking at all, and thus excluded from the scope of the widget.