How many PSI in a full CO2 tank?

Hey guys! I just got my new CO2 tank filled for my kegerator. I was in a jam and had to have it filled on a Saturday... Only place that was available was a place that fills paint gun tanks... Anyhow.. VERY expensive at $40... Normally $25 at gas supply shops..

Well as soon as I got home, i connected my gauge and it was at the "ORDER GAS" red line.. Did I get scammed?? How many PSI should a full tank have? (it is a 4# tank)

My guess is the tank was still very cold from the filling.

CO2 is held in the tank as a liquid, not a gas. As a result the pressure is solely a function of temperature until the tank reaches 10% or so if its rated fill. At that point, the pressure will start to drop.

The high pressure gauges are nice to have, but the only way to know how much you have left is to weigh the tank without the regulator, then subtract the tank's tare weight (stamped on the tank).

By the way, $40 for a 4 lb tank is insane. $25 isn't much better. I live in an urban area in an expensive state and $20 or so gets me 10 lbs at the fire extinguisher shop.