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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The coin has been auctioned 22 times, of which it has sold 12 times. This suggests there is moderate interest in the coin.
- The average hammer price in previous auctions is 29.08 euros, providing a benchmark.
- In past auctions, hammer prices have varied, with some reaching up to 55 euros in the most recent auction.

3. Starting Prices and Estimates:
- The current starting price is 30 euros, which is slightly higher than the average starting price of 27.23 euros. This may indicate that the seller is confident the coin will fetch a higher price.
- Estimated prices in previous auctions have reached up to 150 euros, although this may not be representative of what has actually been paid.

4. Recent Trends: In the most recent auction, the coin sold for 55 euros, suggesting there is potential for an increase in the hammer price.

Based on these factors, an estimated maximum purchase price could be in the range of 40 to 60 euros. This is based on the interest shown in previous auctions and the condition of the coin. A price of 55 euros could be a reasonable target, given that it is the highest price reached recently. However, if a more conservative approach is desired, a limit of 50 euros might be safer.

Therefore, an estimated maximum purchase price could be 55 euros.