How early do you start allowance?

I think 6 years is a good time for starting allowance. To me introducing an allowance not only makes your child understand the value of money it also helps in learning to manage money and applying basic mathematical concepts in real life.
When I started giving allowance to my kid, I also used it as a reinforcement to developed desired behaviors. Now the tricky part is that using allowance to make your child learn about the value of money is one thing and using money as reinforcement to strengthen the desired behavior is an entirely different scenario. Reinforcement has to be gradually reduced and ultimately removed once the behavior is learned.
As for making our young ones realize the value of money, I tried to make my son pay for his favorite snacks, this helped him in establishing a relation between currency and buying favorite things. Similarly, we were used to read the price tags and keep a written price list of the things he commonly used. It made him appreciate the value of money.
You can also introduce the concepts of savings and budgeting as you move ahead. It really makes transition into adolescence easier.

What you are doing sounds amazing. We started with pocked money around the same age and we give the amount that correlates with the child's age. For example my 7 year old gets $7 per week and my 14 year old gets $14 per week. We also have chores that need to be done to earn the money as I have always been a firm believer in you don't get paid for nothing. I also don't pay my kids to clean their own rooms etc. Their jobs are things like picking up dog poo, cleaning the kitchen after dinner and sorting odd socks. I can definitely see that over time this system has worked well. My older children have understandings of the value of money and my younger ones are learning...which is ultimately the goal :)

That's a great idea! He is required to do a certain amount of chores to just get his weekly allowance and we reward him for good grades and certain milestones, but your suggestion is great. I will discuss this with my wife. Thank you!

I think you started giving an allowance to your son at exactly the right age! When the introduction of money is made, usually around the age of kindergarten, kids begin to develop a concept of how money works, so you started right on time! It doesn't mean, as you said, that they understand the value of money, but just the concept of "I have $$ in dollars, I can only do this much with it."

Maybe the concept of how money works, in the real world, could be a help to teach your son the value of a dollar spent, a dollar saved, and a dollar lost. So it may be that having conversations about how the money can be used is a good start. If your son is not too much older than elementary age, there is a really fun book by Allan Kinigus, the "Kid's Activity Book on Money and Finance", which has SO much information, in a kid-friendly format, which could help your son better understand the value of money, not just the concept of it.

Another question is, do you always give your son money when it is tied to chores? There are some financial experts who say that kids' chores should not always require payment from a parent. Rather, doing chores is part of being a family, and contributing to a community. So, what if you were to have a monetary reward system for out-of-the-ordinary chores, but not for everyday ones? I did this with my daughters. When they were growing up, we lived on a large parcel of land, with grandfather oaks, which meant a lot of leaves needing raking each season. This was a monetary chore for them, a hard day of work on a Saturday. Putting their laundry away, or cleaning their shared bathroom, there was no monetary reward, because that was part of living together as a family.