The Yamaha G3 Grand sells for $9000 - $11,000 on today's auction market.
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I used a past sales database, worthpoint.com, to find comparables for your Yamaha G3. It is a subscription site used primarily by dealers, appraisers and collectors.
The comparables were G3's though no year was given. Here we are seeing a mode, or most common number of $9000. I do not recommend selling direct to a dealer, as they will offer 10% - 30% of what they're planned sale price, which does in this case also reach the $9000 range. A dealer's livelihood is dependent on buying for less and selling for as high retail value as possible; the offer is not to offend or 'take' the seller, it is just the nature of the business.
Essentially you can ask any price you please on any object you own, the key factor being finding a willing buyer. If you have a dealer offering to take this from you for $3500, then you get the benefit of them picking it up and handling the transport correctly and also helping a local business owner potentially make a profit in the future. $9000 is the mode price, meaning the most common number coming up for past sales of a Yamaha G3. If you do not feel comfortable asking $9000, then ask what you feel is fair, right and most of all, the price that gets this out the door to complete a sale. There is not a particular market price for a Yamaha piano in Texas as opposed to Ohio, it is not a vernacular collectible and the value is not based on region.