Adding Harry's $200 to the initial value, the bid is at 300 + 200 = $<<300+200=500>>500.
The second bidder doubles the previous value, reaching a value of 500 * 2 = $<<500*2=1000>>1000.
The third bidder adds three times the value of Harry's, then adds 500 * 3 = $<<3*500=1500>>1500
Adding the $1500 to the value of the second bid, the bid is at 1500 + 1000 =$<<1500+1000=2500>>2500.
With the final bid of $4000, Harry bids 4000 - 2500 = $<<4000-2500=1500>>1500 more than the third bidder.
#### 1500