Answer by Professional Japanese Teacher
You can use the above expression to say “It’s cheap”. Yasui means “cheap” in Japanese and yo at the end of the sentence emphasizes the fact that it’s really cheap.
It is also good to know the opposite expression. Takai means “expensive”, so when you hear your customers whispering the word “takai” to themselves, you can quickly say Yasui desuyo.
I hope you will make lots of sales at your stall!