60% of what they will sell it for retail. Look around and see what is selling for used and subtract 40%
Depends on condition and desirability of model
If you're trying to get the most money from your guitar, don't sell it amongst a ton of other guitars, unless it's rare and unique amongst a ton of other guitars.
Sadly little
Not sure. It depends on the condition it is in. I guess you can ask them since they seem to know a lot about instruments.
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