$70 - Maple or Walnut
$80 - Spruce, Koa or Mahogany
$100 - 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.