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 rating of 80 (MS+). This is an important factor, as coins in better condition tend to fetch higher prices.

2. Previous Prices: By looking at previous auction prices for coins with similar conditions (around 80), we can see that they have reached auction prices that vary, but some examples are:
- 2019-09-19: Auction price 15 (condition 80)
- 2018-07-04: Auction price 28 (condition 80)
- 2022-11-16: Auction price not available, but starting price 15 (condition 80)

3. Average Auction Price: The average auction price for this coin is 101.18 euros, indicating that, in general, coins of this reference tend to sell for higher prices.

4. Starting Price: The starting price is 15 euros, suggesting that the auctioneer expects minimal interest in the coin.

5. Recent Trends: In the most recent auctions, the auction prices have varied, but there are examples of similar coins that have reached auction prices of up to 240 euros (2023-03-16, condition 100).

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 60 to 100 euros, considering that the condition is good (80) and there is a history of auction prices suggesting it could reach higher prices in competitive auctions.

Therefore, a reasonable estimated maximum purchase price could be 80 euros.