6K could be a good price for a used Mini 24 however there are 3 important things you need to find out:
- How many watts is the laser source?
- Has the laser source been replaced or serviced?
- The operating hours of the current source?
This will also give you an idea of the condition of the mechanical components and the motors. I don't know what kind of motors Epilog use for these model - brushed or brushless. In general, brushed motors need to be replaced after 6-7 years of active use.
I noticed there is a 30W Zing on sale on eBay in near new condition for 6.2K. It could be a good alternative. The Zing line is equipped with stepper motors. They are not as accurate and fast as the SERVOs in the Mini, but may be good enough for your needs, additionally, they don't require replacement.