Based on the provided data, we can observe that the coin in question has had an average auction closing price of 173.63 euros in previous auctions. Additionally, the current condition of the coin is 80 (VF+).

Considering that the condition of the coin is relatively good and the average auction closing price in previous auctions has been 173.63 euros, we could estimate a maximum purchase price around that value or slightly higher, taking into account the upward trend in prices in recent auctions.

Therefore, an estimated maximum purchase price for this coin in the upcoming auction could be around 180-190 euros. It is important to note that this is just an estimate and the final price could vary depending on demand and other factors in the auction.