In good running shape and clean exterior, Hagerty has these coming in around $10-11k, and will insure them for that amount. But if it needs lots of work, it really comes down to supply and demand and how much someone is willing to pay for it. Which is heavily influenced by the region. They're sparse here on the East Coast, so they go for more. Looks like this one is going to cost a lot to get it to good running shape. You'll have to look into those little rust spots and make sure you can prevent from spreading. So my advice is figure out how much that would be and work backwards.
The 1984–89 Toyota 4Runner is riding high | Hagerty Media