Based on the provided data, we can observe that the coin in question has had an average auction closing price of 82.17 euros in previous auctions. Additionally, the current condition of the coin is 80 (VF+).

Considering that the coin's condition is good and the average auction closing price in previous auctions has been 82.17 euros, we could estimate a maximum purchase price around that value or slightly higher, taking into account the upward trend in closing prices.

Therefore, an estimated maximum purchase price for this coin in the upcoming auction could be around 85-90 euros. It is important to note that this is just an estimate and the final price could vary depending on demand and other factors at the auction.