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), which indicates that it is in fairly good shape, but not the best possible condition.

2. Previous Auction Prices: By looking at the hammer prices from previous auctions for coins with similar conditions, we can see that:
- In recent auctions, coins with conditions ranging from 70 to 80 have had hammer prices between 290 and 400 euros.
- The last auction with a condition of 85 had a hammer price of 396 euros.

3. Starting Price and Average Hammer Price: The current starting price is 300 euros, and the average hammer price in the past has been 295.72 euros. This suggests that the hammer price could be close to this value, but since the condition is slightly better than some of the coins that have sold for less, we can expect a higher price.

4. Market Trends: Given that the coin has been auctioned 92 times and has had a sell-through rate of 94.5%, this indicates consistent demand. Additionally, the fact that it will be auctioned in the coming days may increase interest and, therefore, the price.

Based on these factors, an estimated maximum purchase price could be between 350 and 450 euros. This is because, although the condition is not the highest, there is a price history that suggests it could reach a higher price in a competitive auction.

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