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

1. Current Condition: The coin has a condition 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 of similar coins in the past is 76.73 euros.
- In previous auctions, we have seen hammer prices that varied significantly, but some relevant examples are:
- A coin with a condition of 80 sold for 210 euros in January 2022.
- Another with a condition of 70 sold for 65 euros in October 2022.
- A coin with a condition of 75 sold for 36 euros in October 2018.

3. Starting Price and Average Starting Price: The starting price for this coin is 50 euros, and the average starting price for similar coins is 40.55 euros. This suggests that the starting price is reasonable and could attract bidders.

4. Sales Trends: The coin has sold in 15 of the previous 22 auctions, indicating a consistent interest in this reference.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 150 euros, considering that the condition is good and there are examples of previous sales reaching higher prices. However, since the average hammer price is 76.73 euros, a more conservative price might be around 100 euros, while a more optimistic bidder might be willing to pay up to 150 euros.

Therefore, a reasonable estimated maximum purchase price could be 120 euros.