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 (MBC+), indicating that it is in relatively good shape. This generally translates to a higher price compared to coins in lower conditions.

2. Auction History:
- The average hammer price in previous auctions is 95.25 euros, suggesting that, on average, coins of this reference sell for a price close to this value.
- The last auction with a known hammer price was 140 euros (in 2016), indicating that there is potential to reach higher prices depending on demand.

3. Starting Price and Previous Sales:
- The current starting price is 50 euros, which is relatively low compared to the average hammer price. This may attract more bidders and potentially raise the final price.
- There have been 12 previous auctions, of which 9 resulted in sales, indicating a consistent interest in this coin.

4. Price Trends:
- Observing previous hammer prices, there is a trend for coins in good condition (like the current one) to sell above the starting price.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 120 euros. This is based on the average hammer price and the price history of similar coins in comparable conditions.

Therefore, a reasonable maximum purchase price could be 110 euros.