I just recently bought a Halon 7 which are a little harder to find than the Halon 6. They were going from 500-650 bare bow depending on accessories and conditions. I always advocate selling bare bow as you will make more parting it out. It's more of a pain but it's worth it.
If your bow is in near mint condition with good strings you could start around $575 and the market will dictate what someone is willing to pay for it. I have seen some Halons go for as low as $450.
Here is a really good resource for Mathews bow values on the used market that someone on AT put together.
r.tapatalk.com
Used prices April 2020
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