A friend of my mine was quoted a few months ago $129 for a screen replacement at the Apple Store, she agreed to the fee and they proceeded with the repairs. Less than 10 mins later she was told that the calibration machine wasn't working so they couldn't proceed with the repair and instead were going to swap out the phone with a new phone (a $279 fee) at the same $129 because it was their mistake.
I once took my pc in for a quote to a local pc repairer. I made it quite clear that I only wanted a quote.
At the same Apple Store I took my dad's iPhone 4 in to get checked, he was having battery issues and was out of warranty, I went in to get a quote for a new battery. The Genius said that it might not be a battery issue but had no way of knowing for sure, he suggested putting in a new battery to see if that would fix the issue.
I said he can open it and try a new battery, but at no point did I agree to a repair fee. He put in a new battery and it was finally able to charge more than 50%, then he gave me a bill for $80. I refused to pay because I went in for a quote, he suggested trying a battery first before I agreed to the fee but he ended up glueing the battery inside making it unable to remove it, and me having not agreed to any fees prior I got a free battery (well, my dad did).