By default, Vendor role prohibits to edit, create and delete rates in the contractor editing form. However, you can easily change this behavior and allow contractors to edit their prices.
How to allow to create, edit or delete prices
Open Vendor role, switch to Type permissions tab and double click on Contractor's default price row:
Change Write, Create and Delete permissions to Allow according your preferences.
How to allow to create prices, but deny edit and delete prices
1. Open Vendor role, switch to Type permissions tab and double click on Contractor's default price row, as in example above.
2. Change Write and Create permissions to Allow.
3. Then, add a new row to the Member permissions table and deny write access to objects which are not new. This will require to add the following criteria:
In the Members property select all properties.
In a such way, contractors will get write access to own prices, but this wrote access will be denied for not new objects (in other words, for objects which were previously saved), and allowed for new objects, which means that contractor can create and edit new prices, but can't edit/delete old prices.