Local prices on custom made metal railing seem extremely high to me.

Yes. Market price of aluminum shapes is around $1.20/lb these days. You
will pay several times that at a distributor for the unfabricated stock.
And this will factor up again with fabrication.

Down here in Florida you have to have code-approved aluminum hurricane
shutters. These are nothing more than a $3 stock sheet of aluminum from
Alcoa run through a machine that puts a few corrugating bends in, a few
holes punched, and priced at about 20X the input sheet. What a racket.