Next time you get a call, try this:
"So I won xxx price?"
"How much did you say it is worth?"
"Did you say I have to attend a 2 hour seminar?"
"Since I've won the prize, can you have a courier send it down to my office at ...."
"I'm sorry but I'll forgo the prize as it's not worth it. I make $800/ hr. If I take 2 hours to come down, I'll be losing $1.6k to get your prize worth $xxx. If you're truely interested in having me come down, how about you send me a cash cheque for $1.6K and I'll take 2 hours to come down to your seminar?"