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 quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Previous Auction Prices:
- The coin has had a hammer price of 112.8 in a previous auction, although the condition of that coin is not specified.
- In other auctions, hammer prices have varied, but the average hammer price is 60.69 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 30 euros, which is below the average starting price of 40.65 euros. This could indicate potential for an increase in the hammer price.

4. Sales Trends: Of the 8 times it has been auctioned, it has sold 5 times, suggesting there is interest in the coin.

5. Previous Estimates: In the most recent auction, the estimated price was 35 euros, which can also serve as a reference.

Taking all these factors into account, an estimated maximum purchase price could be set in a range that reflects both the condition of the coin and previous hammer prices.

Given that the condition is good and there is a history of hammer prices exceeding the current starting price, a reasonable maximum purchase price could be:

Estimated maximum purchase price: 70 euros.

This price reflects a balance between the condition, interest in the coin, and previous hammer prices.