As pricing changes for products over time, the project templates will not get updated automatically. To ensure your projects are being forecast correctly, use the Recost all Templates button on the project template dashboard. Administration -> Project Templates.
Note: Your actuals on a project, timesheets, stock usage or purchase orders, will always be the current FIFO landed cost or base rate. Updating costings on your templates is only changing the the forecast costs applied to a project from the template.