The difference is the price, no? If I get paid 100 for playing a concert on one day, but 120 another day, did I get more productive? Either way I produced the

The difference is the price, no? If I get paid 100 for playing a concert on one day, but 120 another day, did I get more productive? Either way I produced the same number of concerts, but got 20% more payment. Measured in concerts my productivity was the same. Measured in other goods it went up.