One company sells the glasses for $40 each. And company two sells the same glasses at 4 for$140. How much will they save if they use company 2?
If company two sells 4 glasses for $140, the price per glass sold by company two is $140/4 = $<<140/4=35>>35.
Therefore, using company two will save them $40 - $35 = $<<40-35=5>>5 per glass.
So if they buy four glasses, they will save a total of $5*4 = $<<5*4=20>>20. Answer: \boxed{20}.