Common expressions - Shopping

Hi guys, could you help with these questions?
What are the most common expressions, the daily use ones, used when you are shopping?

1. You are at a store and find something you like and you want to buy it, what do you say?
"I am buying/ 'll buy this? " "I'll take this." This would be the most common when you are telling the salesgirl. "Wrap it." is another way of saying.

2. What phrases do you usually use when you want to discuss the price of something?

"it's too expensive/cheap", "Can I afford this?", "You gotto be kidding!", "What a bargain/steal", "Just what I'm looking for."

Please help me correcting what I wrote above and if possible writing down here any other usefull shopping language.

Thank you for your time.