I am going to steal something from a shop.
Is this an item your gonna keep and it's very expensive?
Yes I'm not going to give it back
No matter what you think, stealing is wrong. You shouldn't take away the hard work of all the people who were able to bring that product to you, and you're not paying them for it.
I know, but I also knew that I'm not going to give it back so why not just take it.
Because it is stealing. Stealing is wrong and if it's expensive as you say, it could be a felony. Just save up to buy it.