To estimate a maximum purchase price for the coin with a grade of 80 (MBC+), we can analyze the historical data from previous auctions of coins with a similar grade and their hammer prices.

1. Relevant data from previous auctions:
- Coins with a grade of 80 (MBC+) have been auctioned several times. Some examples are:
- 2012-02-22: Hammer price 350 (grade 80)
- 2012-04-29: Hammer price not available (grade 80)
- 2012-12-01: Hammer price 373.37 (grade 80)
- 2019-05-29: Hammer price 680 (grade 75)
- 2023-03-22: Hammer price 360 (grade 75)

2. Price analysis:
- The highest hammer price for a grade of 80 (MBC+) was 680 euros.
- The lowest hammer price in this range was 350 euros.
- The general trend shows that hammer prices for similar grades range between 350 and 680 euros.

3. Additional considerations:
- The average hammer price for this particular coin is 1035.52 euros, indicating that, although there are examples of lower prices, the market may be willing to pay more for coins of this reference.
- Given that the coin has a starting price of 500 euros, it is reasonable to consider that the hammer price could be above this value, especially if there is interest in the auction.

4. Final estimation:
- Taking all these factors into account, an estimated maximum purchase price for this coin with a grade of 80 (MBC+) could be in the range of 600 to 800 euros. This is based on previous hammer prices and potential interest in the auction.

Therefore, a reasonable maximum purchase price could be 800 euros.

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 a medium-low state. This generally affects the price, as coins in better condition tend to fetch higher prices.

2. Current Starting Price and Historical Prices: The current starting price is 150 euros, and the average starting price in previous auctions is 389.49 euros, with an average hammer price of 534.64 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 97 times, of which it has sold 77 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 (75), we can see that they have reached hammer prices that vary, but some have been quite high (for example, 595.61 euros in 2012).

5. Recent Trends: In the most recent auctions, hammer prices have shown a trend of being higher, which could indicate an increase in demand or in the value of the coin.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 300 to 450 euros. This is based on the average hammer price of similar coins and the historical hammer price data for coins in similar conditions.

Therefore, a reasonable maximum purchase price could be approximately 400 euros.