Sounds expensive! Don't know what the hourly rate for bike shops is . In UK it's about £30-40p.h.
there is no way it's 3+ hours work.
I can dismantle,clean,,check and regrease an8speed hub in an hour, comfortable.
A straight swap with an quick inspection and regrease is 1/2hr.
Something most LBS should easily attain, provided,they have a technician with hub gear experience.