Bob on...
First and foremost, I'm what's known as a 'collector' DJ, however I take each spot seriously and because of this I have four different boxes of records for DJing that are pulled seperate from the collection...
That way, no matter what the style of music played I can usually grab one or two and do right by the promoter and their crowds tastes.
I also collect for myself, and 90% of the records I buy arent suitable for playing out - I know that, so I leave them at home.
Unfortunately some 'collector' DJs insist on taking them out and giving them a try anyway.
Price is immaterial, but I do agree that if I hear a DJ play a spot I could listen to at home on original vinyl, then I start to get bored...