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

1. Current 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 similar coins has been 80.12 euros.
- In previous auctions, we have seen hammer prices ranging from 46 euros to 160 euros, depending on the condition and other factors.
- The last auction with a condition of 80 had a hammer price of 80 euros.

3. Starting Price: The starting price is 50 euros, which can be a good indicator of the sales expectation, but not necessarily of the final price.

4. Price Trends: In recent auctions, hammer prices for coins with similar conditions have been around 80-100 euros.

Based on this data, an estimated maximum purchase price could be in the range of 90 to 110 euros, considering that the condition is good and that the price history shows that coins in similar conditions have reached hammer prices in that range.

Therefore, a reasonable estimated maximum purchase price could be 100 euros.