If it's an inherited tree, you may not be familiar with what people look for in higher-end trees or bonsai. Trees handed down to relatives are sometimes overvalued for many reasons. Sometimes trees are overvalued by their original owners. The actual market for them usually brings a reality check for the legacy owner, unfortunately.
This tree has some big issues. The foliage, for instance, is all at the ends of long branching. That's a problem for junipers and conifers in general that haven't been worked adequately over a period of time. Conifers can't be quickly overhauled with heavy pruning like deciduous trees. You can't prune off all the foliage on a conifer's limbs because it will kill the limb. It will take years to either prune to induce foliage closer to the trunk or grafting on new foliage. The foliage should be only inches from the trunk to make the tree more compact in appearance. Grafting new branching on the bare portions is probably the way to go here, instead of trying to induce backbudding by pinching the existing growth. That's a lot of work and will take years to accomplish.
The tree's roots look to be pretty packed into the large container. That's another problem that can take years to correct. Have you looked at the roots by slightly lifting the tree from the pot, or repotted the tree? Understanding what the root mass under the soil looks like is important because it can prevent issues that can compromise the tree's health.
Also, generally a tree in that price range should come with a decent pot. It's not a huge deal, but mica pots are generally used for grow pots for developing material not for high end trees.
All in all, this tree will require quite an overhaul to bring it back to the $4,000 range and I think if it's worked correctly over time, it COULD be in that range, given the substantial trunk and visual
movement in the trunk and nebari.
The competition for pricey higher end bonsai is quite stiff. For that money, a buyer can get a very nice collected tree or even an exhibit quality tree from well-known sellers.
I think the advice to take this to a local bonsai club and get some informed opinions on what can be done is good. You may even find a buyer, but i wouldn't expect to get more than $200 for this as-is. If you have the time to correct the issues (which might take five or more years), it could inch into the +$1,000 range.