I don't want to pay for the blouse before I leave the store.
That's bad. Why would you do this?
I think that it is too expensive for me to buy!
I think that you should either pay for it, or look for a cheaper option. It is expected that you will pay for the things that you want in life.
I just want to take the fucking blouse and I'll pay for it later.
That is not the way things work. People expect to pay for the items right away unless the store has the option to put it on layway.