Depends in which condition, how old and how much used. I would pay much less for a machine which strung 5000+ rackets compared to machine which just strung around 1000 rackets. We need more detailed informations. From 1000GBP to 2500GBP is anything possible. BTW, I wouldn't go for a machine with fixed towers which is designed for tennis. Less to none adjustments.
If it's first hand, the owner must know something about it. Not the exact number of rackets but a range. It's also important to verify anything with the invoice. Is he a shop owner or a normal person? If I were you I would make an appointment with the owner and bring a racket, to test drive. If something is strange on a 32lbs job, I would be sceptical. If you can string a racket at the owner without any issue, the machine seems to be OK. Look for small scratches, dust etc. which can tell you something about the treatment and usage.
