Which BI solutions cooperate with Postgres database and aren't too expensive?
If you are comfortable with excel you could import the data directly with an odbc connection. 

If you wanted olap capability you can do that with a tabular model within excel. 

In general most BI solutions will work with any relational database via an OLE or ODBC connection. If the product doesnt have a native adapter you could use a 3rd party ETL tool to move the raw data to a db that is supported.