It sounds like he is a purchasing predator who knows his stuff but just does this stuff to get the price down further n further.

Once u shake a mans hand, agree on a price, THAT IS THE PRICE ! Story over, no exclusions ever !
When people do anything else but that, they really are showing their low class and a huge lack of credibility and honour, and it really hits a red flag for their overall personality.

Next time get him to call 1800 333 555 (Lifeline-someone who might care) lol