Here are the starting prices for various ct weights from the Tiffany website:
Round:
0.25ct - $1700
0.50ct -$3200
1ct -$9200
1.5ct -$16,700
2ct - $28,200
2.5ct -$38,700
Princess:
0.50ct - $3250
1ct - $8900
1.5ct - $16,000
2ct - $25,400
2.5ct - $34,300
Pear:
0.50ct - $4050
1ct - $8450
1.5ct -$16,700
2ct - $25,400
2.5ct - $34,700
Heart:
0.50ct -$4320
1ct - $10,200
1.5ct - $19,200
2ct - $28,700
2.5ct -$39,500