To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Condition: The coin has a condition rating of 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for coins with a similar condition (80) has been approximately 38.08 euros.
- In previous auctions, hammer prices for coins with a condition of 80 have varied, but the range has been between 25 and 65 euros.

3. Starting Price: The starting price is 30 euros, which is a good indicator that the seller expects considerable interest in the coin.

4. Sales Trends: Out of the 17 times it has been auctioned, 14 have been sold, indicating good demand.

5. Previous Prices: In past auctions, the highest hammer price for coins with a condition of 80 has been 65 euros, which can serve as a benchmark.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 60-70 euros. This is based on the hammer price history and the condition of the coin. However, it is important to remember that the final price may vary depending on the competition in the auction and the interest from other buyers.