A few observations on the available Red Chests:
1) The first one, on the roof of the building where the bus drops the player off at the start of the game, generally contains average-quality weapons up to Level 7 (ish), after this, they tend to stall as basic Jakobs sniper rifles.
2) The crate on the cliff-side bandit camp in Arid Badlands, the site of Scavenger: Combat Rifle, has another, which is in the highest, furthest-right shack. This crate usually contains some excellent weapons: eg, four Level 22 Class Mods at Level 13, a blue-rarity rocket launcher at Level 24, and on one occasion, a purple rarity Sniper Rifle dealing 215 damage at Level 13.
Between these two, in twenty minutes I made more than $15,00.