To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in an acceptable state, but not of the highest quality.

2. Auction History:
- The average hammer price for similar coins has been 556.76 euros.
- In previous auctions, coins with similar conditions (75) have had hammer prices that varied, but some examples are:
- 2019-09-19: 280 euros (condition 75)
- 2020-07-08: 225 euros (condition 75)
- 2023-01-31: 340 euros (condition 75)
- The highest recorded price for a coin in similar condition was 650 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 300 euros, which is below the average starting price of 393.06 euros.

4. Recent Trends:
- In the most recent auctions, hammer prices have shown a trend of being in the range of 300 to 600 euros for similar conditions.

Based on this data, an estimated maximum purchase price for the coin could be in the range of 500 to 650 euros, considering that the condition is acceptable and that the price history shows that similar coins have reached those values.

Therefore, a reasonable maximum purchase price could be 600 euros.