@Fari
Just use comparison. Generally if you are in a store and you know which product is for what, then you can make a guess based on relativity. if you see a pack of soap for 500 neurogiggles , a pack of cigarettes for 1200 neurogiggles and a car for 600000 neurogiggles then you might guess that generally a neurogiggle is about 1 to 3 dollars and that soap might be overpriced!
That's how people win The Price Is Right Of course that is a blatant ballpark example and in a general store you'd see much closer prices, thus making it easier to narrow down possibilities, cars can vary a lot.......
There are many languages where numbers aren't hard to figure out. If the otherworld's tongue is something along the lines of Arabic or Hebrew then maybe there'd be trouble, but that doesn't have to be the case. Even Japanese makes use of rather simple number symbols (nowadays they are moving more and more towards roman numerals though).