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 75 (MBC), indicating that it is in relatively good shape, but not among the highest qualities.

2. Auction History:
- The average hammer price for similar coins in the past is 113.11 euros.
- The coin has been auctioned 12 times, of which it has sold 9 times, indicating good demand.
- Previous hammer prices for coins with similar conditions (75 and 80) have varied, but recent auctions have seen hammer prices of up to 85 euros.

3. Starting Price: The starting price is 30 euros, which may attract more bidders, but it could also indicate that the seller expects a lower price initially.

4. Price Trends: In previous auctions, hammer prices have ranged from 14 to 430 euros, depending on the condition and demand at that time.

Given that the coin's condition is 75 and considering the hammer price history, an estimated maximum purchase price could be in the range of 80 to 120 euros. However, since the average hammer price is 113.11 euros, a reasonable maximum purchase price could be:

Estimated maximum purchase price: 100 euros.

This price takes into account the current condition and price history, providing a margin for competition in the auction.