At the shop I'm using now, pricing is ala carte, so it doesn't matter if you buy the ball there or not, drilling fees are the same.
$50 for drilling, $10 for a custom drilled thumb slug, and $5 a piece for finger inserts.
$70 total. And it ALWAYS fits.
I cant say I don't buy online, cause sometimes I do, but lately its only been hard to find stuff he cant get anymore, or something so crazy cheap you cant pass it up.
Otherwise, I buy from him.