when I overhaul and engine,I spend quite a lot on machine work.Im fussy and have to pay the price. The block gets cleaned(several times if you count thread chasing)new cam bearings and frost plugs.
Machine work is align hone as required,bore as required,finish hone as required,squared and decked.crank gets ground and or honed. heads get resurfaced,valve grind and guides as required.rods are magnafluxed/resized.rotating parts all get "precision" balanced.some blocks require clearancing,,,
The machine shop guy gets a few bucks
The better quality the machining the more the cost,,,