Couple of things about medieval armor.

No, mail (maille) was not exclusively for the wealthy.  Depending on period and location, it was considered standard issue for a professional soldier.  It wasn't cheap though.

On names - "chain mail" is redundant.  It's "mail" or "maille".  "Scale mail" is a misnomer - it's just scale or scale armor. There were MANY variations on the basic scale theme, like coat-of-plates, lamellar, etc.  Styles varied widely with period and region.  And no, mail wasn't useless against armor-piercing arrows or bolts, just less useful.

Pick up a few of Osprey Publishing's excellent series of illustrated books for plenty of info on medieval armor.

Leather armor was often (usually?) what the French called "cuir bolli," hardened via some kind of boiling process.

Odd factoid, the Mongols used a form of silk "armor" bundled thickly about themselves - when pierced with an arrow it would (hopefully) sink into the wound around the arrowhead and facilitate removal and minimize the damage.