I assume that the average person is a commoner, from 1st level in the mid teens to maybe 8th or 9th in thier 60s, and people who've had rougher lives are higher level. Everyone gains levels as they age, but are all NPC classes. Green soldiers are 1st level warriors, veterans are maybe 4th/5th level, and elites are 10th and up. Heck, bouncers at bars tend to be 2nd or 3rd level warriors. Nobles are either experts or aristocrats, or multiclass as both, and tend to have higher levels to represent a lot of training.
But magically, very few people are actually spellcasters. The average priest is an expert, the rare one an adept, and only special mystic knights are actually clerics. Eberron describes the situation perfectly.
Arcane casters are recovering from a purge in the main play area and are still rather rare, but the few wizards around tend to be powerful, as the weaker ones either get more powerful or die, so 7th level is avareage I'd say, with the limit going all the way to epic levels.
Now, the large continental empire has a much higher concentration if power, and there you'll find actual epic level fighters as generals, and an area where the nobility is all sorceres of power from mid teens to high epic, so there are large variations in power level.