I recommend reading this post from the Podiatry Today blog, written by Dr. Douglas Richie Jr., D.P.M.: Are You Really Getting A Custom Foot Orthotic? | Podiatry Today

Whereas designing a custom foot orthotic used to involve meticulous attention to the individual patients needs, modern technology and lack of sufficient reimbursement have led many podiatric labs to provide over-the-counter foot orthotics at a custom orthotic price. The outcome may or may not be sufficient for the individual patients needs.