What exactly is purchasing power parity (PPP)?
What you are describing is basically purchasing power. Purchasing Power Parity (PPP) claims that your purchasing power is the same across countries.

PPP states that, if say a pound of bread costs 4 US$, you can take that amount, exchange it to Chinese yuan, go to China and buy exactly the same amount of bread. (i.e. you have the same purchasing power in both countries)

3 factors play a role: the price (of bread) in the US, the price in China, and the Exchange rate. There is no subjective factor here.

Even though I don't fully understand what you mean by "purchasing labor", make sure that you compare goods, or baskets of goods, only (PPP does not say anything about wages or production costs).

And be sure to remember that PPP does not necessarily have to hold in reality.

Hope this helps!