i had looked into new glass tanks when i did this (2006). insane is a good description of what the cost was.
i also looked into moeller plastic tanks but at the time they didn't offer any tank large enough.
aluminum is what i went with and the exterior is coated. i think it was powder coated but i would have to dig up the paperwork to verify what was used.
everyone i know who went thru this, ended up with aluminum. for all the sportfisherman boats the back deck had to come out too..