We have found that customers need to have security on costs. So, there are users that has to watch prices but not costs, or perhaps nor prices nor costs. This is no possible so this values are stored in price lists, estimates and actuals, and if you apply field security to one of the fields involved (price, amount, etc) the process of Entering and approving time entries doesn't works. 

It would be great to be able to apply field security on entities of the PSA, or at least some workarround to hide costs from the CRM (advanced search included)