This article is from the Audio Professional FAQ, by with numerous contributions by Gabe M. Wiener others.
Depends on what you want to have done, and where.
One can pay upwards of $300/hr for prime studio rental time in New
York. In a small community however, one might find a project studio
for $25/hr. Generally speaking, the rule is: the rarer the service,
the more it will cost. In a community with dozens of small 8-track
studios, you won't have to pay much. If you need emergency audio
restoration, or mastering by a top-flight pop-music engineer, you
can expect to drop many hundreds of dollars an hour. Like so many
other things in this industry, there are no rules, and Smith's
invisible hand guides the market. [Gabe]
 
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