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+). This is an important factor, as coins in better condition tend to fetch higher prices.

2. Current Starting Price and Previous Prices: The current starting price is 30 euros, and the average hammer price in previous auctions is 110.79 euros. This suggests that, in general, coins of this reference tend to sell for significantly higher prices than their starting price.

3. Sales History: The coin has been auctioned 112 times, of which it has sold 90 times. This indicates good demand and a history of successful sales.

4. Previous Hammer Prices: Looking at previous hammer prices for coins with a similar condition (80), we can see that they have reached hammer prices of up to 110 euros in the past.

5. Recent Trends: In the most recent auctions, hammer prices have varied, but there are examples of coins with similar conditions that have sold for over 100 euros.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 100 to 120 euros, considering that the average hammer price is 110.79 euros and that the condition is good. However, since the starting price is 30 euros, it is likely that buyers will be willing to bid beyond this initial price, especially if there is interest in the coin.

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