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 an acceptable state, but not among the best qualities. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Starting Price and Average Hammer Price: The current starting price is 2200 euros, and the average hammer price in previous auctions is 2433.73 euros. This suggests that, generally, coins of this reference tend to sell for above the starting price.

3. Auction History: By observing previous hammer prices, we can see that they have varied considerably depending on the condition. For example, in past auctions, hammer prices have reached up to 6000 euros for coins in better condition (such as those with a condition rating of 95).

4. Price Trends: The average hammer price of 2433.73 euros is a good indicator of what can be expected. However, given that the current condition is 75, it is reasonable to adjust expectations downward.

5. Comparison with Previous Prices: The last auction with a starting price of 2200 euros and an estimated price of 3000 euros suggests that there is potential for an increase in the hammer price, especially if there is interest in the coin.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 2500 to 2800 euros. This is based on the average hammer price and the current condition, as well as the potential interest from collectors.

Therefore, a reasonable maximum purchase price could be approximately 2700 euros.