Re:how much does balancing cost?
+1 x 1000 for dynamic balancing, record ALL your measurements and weights so if you end up replacing parts later you can keep in the specs.
As to cost, thats situational for many reasons. One is the skill of the balancing person, as its a bit of a science and black art. Secondly is what kind of issues they have to deal with.
It might be easy to balance but some can be really challenging even by a expert. Also,, depends on the job itself. a FULL WIDTH Flywheel is easiest as there is material to remove to balance, but cut down flywheels are more challenging. In some cases the area to remove weight does not exist so the only alternative is add Mallory metal to even it up.
Im in the US but my old crank guy, Dan Halls 5 point automotive would charge $150 to $250 for the balancing alone. However my main guy, EV Lewis,, was typically $75 to 150 unless he had to add Mallory metal or other problems. If you included them he also would do timing gears, trans main and lay shafts, clutch baskets and Alternator rotors and often CHEAP! $10 each item.
But 100% worth it. Every penny. Ive worked in manufacturing, My wife does as well. Everything has a tolerance, and "Close enough is good enough" is the mantra for most everything. British factories back in their day had a low margin of profit and many were struggling to stay afloat, so many items were built to a cost. Thats not an insult,, but simply reality and any company worldwide had that issue.