You bet is pretty common and casual. I don't know what planted conceited in your mind.
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CliveWhere I live, we usually do not feel it necessary to respond to 'You're welcome'.This puzzles me. You bet is another way to say You're welcome, not a response to it.
CalifJimI've never heard it on either coast."You bet" for "You're welcome" is not uncommon around here, but it is a tad WWII.