$55 - Maple or Walnut
$65 - Spruce, Koa or Mahogany
$85 - Rosewood or Cocobolo
For sizes other than for a 4 inch soundhole add $16.
The vast majority of steel-string guitar soundholes are 4 inch in diameter (101mm). Most nylon-string (classical guitars) have 3 1/2" (89mm) soundholes. To determine your soundhole size just measure the distance across the center of your soundhole.