$150/hole x 6 holes = $900 using my math.
I paid $1250 to have all 6 holes sleeved 2 years ago on a 401 block. That cost included the price of the sleeves at $50/hole. This operation was a "double bore", meaning the block was bored once for the installation of thick wall sleeves, and then bored and honed a second time to fit the standard pistons. My machinist does very good work, and I thought that price was fair.