title: Laravel: How to sync pivot data with checkboxes
body: <p>I have 2 tables: jewels and materials and a pivot table jewel_material with an extra price field.
  What I would like to achieve is that the administrator can choose by checkboxes in what materials a jewel will be performed.
  For the chosen materials a price must be given.
  Making work the checkboxes for the materials was no problem. The additional price field is...
  I suppose that I have to put associative input fields in the form with the material_id and the price, but I really don't know how to do it...</p>