I often get calls from collectors that want to sell their artifacts or get values. Sellers need to know values are difficult to determine without actually viewing the artifacts. A slight chip or crack can devalue an artifact by many dollars. Sellers also need to know that in today's market common artifacts have dropped in value. Unique artifacts with good provenance have by enlarge maintained value. What I suggest sellers to do is take good pictures and measurements. Provide a description of the artifact(s) such as where it was found, provenance of the piece (what collection it came from) and any useful information. At least that way a general sense of value can be determined.
Sellers should realize that there are two kinds of buyers. One buyer wants an artifact for their personal collection and the other wants to resell the artifact. Usually a collector will pay more for good pieces while the reseller needs to make a profit and may offer less.
Feel free to contact me with any questions you may have.
Aloha, Steve