To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including the current condition of the coin, previous auction prices, and behavior in past auctions.

1. Current Condition: The coin has a condition rating of 80 (MS+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Auction Prices:
- The average auction prices for coins with a similar condition (80) in the past have been approximately 1,066 euros.
- Auction prices for coins with a condition of 80 have varied, but there have been auctions reaching up to 1,300 euros in previous sales.

3. Starting Price: The starting price is 750 euros, which is reasonable compared to previous auction prices.

4. Auction Trends: The coin has been auctioned 16 times, of which 14 have sold. This indicates a consistent interest in the coin, which may influence the final auction price.

5. Maximum Price Estimate: Given that the average auction price has been 1,066 euros and considering the condition is 80, a reasonable maximum purchase price could be in the range of 1,200 to 1,400 euros, based on previous auction prices for coins of similar condition.

Therefore, an estimated maximum purchase price for this coin could be 1,300 euros. This is based on historical behavior and the current condition of the coin.