Cleaning the interior of a piano is not something clients always think of doing. However, it is still part of the regular maintenance of your piano. Though a dirty piano may not necessarily affect the playability of your piano , it certainly does affect how it looks in your home. Under more severe circumstances, it may even affect the, value, tone, and playability of your instrument when there is an excess accumulation of dust and grime. Cleaning a piano may seem like a simple task that the client decides they can do themselves. In a lot of way's it is. However, there are a few dangers involved when doing this. For example, the soundboard of many pianos may have delicate finishes on them. So one would want to be very careful so as not to accidentally create a scratch. Even getting under the strings to clean can be a bit tedious. Also, removing the piano action has it's hazards. You would be very careful about pulling out any grand action as you could easily damage the hammers.
Therefore, it is recommended hiring a professional to clean your piano as they have both the proper tools, knowledge, and experience necessary to clean your piano effectively and safely.
I charge on an hourly basis for cleaning ($40/hr). Most pianos take around 1 hour, (unless your piano is exceptionally dirty.) :P