For most people off the shelf insoles will do. I think some “podiatrists” like to over sell custom insoles even though there is a little evidence to suggest that they are any better than off the shelf ones.
I am one of those people who has hand made insoles from a Podiatrist, and yes recently they set me back £150 a pair. I initially got a pair on the NHS back in 1993 and they cost me a princely sum of £0-00.
I can only go off the little evidence, as in my own personal experience, and say that for me the insoles are worth every penny.
Before I had the insoles made in 1993, I used to have severe knee pain in both knees. Even walking up stairs was painful. However with a biomechanical assessment of the way I walk, by a physio and podiatrist, it was agreed by both medical professionals that I would benefit from bespoke prosthetics, made for free on the NHS. The only reason I bought a further pair 24 years later was that the NHS was rammed busy and my old podiatrist had gone private and I liked what he did for me all those years ago.
For anybody who is referred by a physio and a podiatrist then I believe that bespoke prosthetics in their shoes will greatly enhance their quality of life by reducing knee pain fairly quickly.
As for people with no medical reason for hand made prosthetic insoles, I highly recommend footreviver insoles. I have a pair in all my shoes and boots.