Avoid saying thank you at the beginning of your event. That being said, a short warm welcome is always appropriate when opening your live auction festivities. It should be followed directly with an invitation to begin the auction. There should be no thank you’s interspersed with the auction activities.
When the festivities have come to an end, you can say thanks for everyone’s bidding generosity. You can also thank individuals with a sincere handshake or a hug where appropriate. Everyone should be made to feel that their attendance is warmly appreciated and that you look forward to seeing them again at your next event.