Vintage Synth Repair

Hi everyone,
Hope you may be able to help. My friend has finally agreed to sell  
his G101 organ. The organ is in very good shape and plays wonderful. 
The only repair it needs is minor, a wire has broke loose from the 
line out jack and needs to be re-soldered. I've offered him a fair 
market price but he feels it's worth more. So, I was hoping that you 
may prvide some figures in black and white, so he can see for himself. 
Not trying to steal it from him, but don't want to over pay...... Your 
thoughts?
Thanks! Ray