To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current Condition: The coin has a condition of 80 (MBC+), indicating that it is in relatively good shape. This suggests that its value should be in the upper range of previous auction prices.

2. Previous Auction Prices: By observing previous auction prices, we can see that coins with similar conditions have reached auction prices that vary, but generally, the auction prices have been in the range of 1,200 to 1,650 euros for conditions of 80 and 85.

3. Average Auction Price: The average auction price for this coin is 1,345.13 euros, which can also serve as a reference.

4. Auction Trends: The coin has been auctioned 17 times, of which 16 have sold. This indicates good demand and sustained interest in the coin.

5. Starting Price: The starting price is 1,500 euros, which is slightly higher than the average auction price. This may be an indicator that the seller expects good interest in the auction.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 1,600 to 1,800 euros. This is based on the current condition, previous auction prices, and interest in the coin.

Therefore, a reasonable maximum purchase price could be 1,700 euros.