I have tried bargain brands in the past and quickly learned my lesson.

The revelation came to me when I bought a "bargain" Oxy Clean type product. When I clean with real Oxy Clean I can see the white marks on my skin from the basic pH chemicals reacting with my skin. When using the bargain product I didn't notice the reaction on my clothing or my hands. Even though it only cost me $2, I took it back to the store because I was insulted.

I don't buy bargain lemon juice, but I can sure tell if it is diluted. I dilute the lemon juice I buy because the real stuff is so strong that I can dilute it in a large container and get a lot of lemonade. If the ingredients of lemon juice list too many preservatives and flavor enhancers then its probably diluted (more salts than lemon juice).