QUOTE(The Wiki)
The amount of experience gained depends the level of the materials used for the upgrade: +2 per low-grade, +10 per mid-grade, and +40 per high-grade; this means an effective cap of 250? per upgrade. It is not affected by bindings or rare materials used.
The amount of EXP that will be gained is shown when hovering over an upgrade.
QUOTE(The Game)
Grants 370 Forge Exp and 37 Gear Potency
This is for both my rapier and my armor at Coruscating Catalyst levels. The wiki is badly wrong. No wonder I made it to Forge 50 with room to spare. Perhaps it is +60 per high-grade material? Nope, I checked on some lower upgrades and that's too much. Maybe the catalyst is giving a lot of forge exp.