Based on the data provided, we can observe that the coin in question has had an average auction price of 143.19 euros in previous auctions. Additionally, the condition of the coin on this occasion is 70 (VF+).

Considering that the condition of the coin is relatively good (70), and that the average auction price in previous auctions has been 143.19 euros, we could estimate a maximum purchase price around that value or slightly higher.

Given that the coin will be auctioned in the coming days with a starting price of 15 euros, we could consider an estimated maximum purchase price range between 140 and 150 euros, depending on demand and other factors that may influence the auction.

It is important to note that the final auction price may vary, and it is advisable to closely monitor its progress to adjust the offer accordingly.