Based on the data provided, we can observe that the coin in question has had an average auction closing price of 72.41 euros in previous auctions. Additionally, the current condition of the coin is graded at 70 (VF+), indicating that it is in an acceptable condition.

Considering that the starting price for the upcoming auction is 30 euros and the historical average closing price is 72.41 euros, we could estimate a maximum purchase price around that value. However, taking into account that the coin's condition is graded at 70 (VF+), which is acceptable but not excellent, we may slightly adjust that price downwards.

Therefore, an estimated maximum purchase price for this coin in the upcoming auction could be around 70-75 euros, considering the condition and historical closing prices. It is important to note that the final price will depend on the demand at the auction and other potential interested buyers.