To sell a product or service to someone at the same or close to what the product or service will cost you. Hence the person that you are selling to is being given a substantial discount on the normal price. As the term "mates rates" suggests this level of discount is usually only given to mates, or friends, of the person selling the product or service.

Bob: "Hey Johnno, how much did you pay for that computer?"
John: "Got it real cheap mate. Trev sold it to me at mates rates."
by M Provost December 27, 2005
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someone who will only hang out with you if they have nothing to do, and are very bored. usually apart from this they will rarley speak to you
Jenny's new boyfriend was busy on saturday so she relied on her second rate mate to watch a movie with her.

whenever im bored i can rely on my second rate mate rob to come over and keep me company
by lifes.two.short May 7, 2006
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