Machine shop prices are all over so it's hard to say "this, that" for any particular situation. Here, because there are almost no performance shops at all it is a better total investment to buy a kit with everything and then take your block in to get it prepped. There's one shop left that grinds cranks and he doesn't do it very often. Most others closed down/retired. And the one good shop does mostly resto work and diesel repair - few people do their own thing anymore. They go buy a crate motor.
I spent $2400 on a 393C racing level kit - name brand H beam rods, pistons, steel crank, rings, bearings, etc. I already had a decked and bored block. Sent they guy my black deck measure and requested deck clearance (.005) and all I needed to do was have the block honed out another .001. Bolted it all in and made 575 HP with it. The point being that working with a good vendor will get you parts that work right out of the box, vs running around getting this and that done, collecting parts, going back and paying to have it all balanced, etc.
Heads are another thing - depends on the amount of work they need. You quickly reach a tipping point where you are money and power generation ahead to just buy modern units. Simple valve job/update, stocker level cam/springs, etc likely no problem. You start to step up and you should be tossing every bit of OEM valve train equipment.
