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

2. Auction History:
- The average hammer price for this coin has been 47.06 euros.
- In previous auctions, the hammer price has varied, but there are examples of sales reaching up to 220 euros in a recent auction (although that coin had a condition rating of 90).

3. Starting Price and Estimated Price:
- The current starting price is 30 euros, and the average starting price in the past has been 20.73 euros.
- The estimated price for this auction has not been provided, but in previous auctions, the estimated price has been up to 50 euros.

4. Sales Trends: The coin has been auctioned 23 times, of which 18 have been sold, indicating good demand.

Based on this data, a reasonable maximum purchase price could be in the range of 70 to 90 euros, considering that the condition is 75 and the average hammer price has been 47.06 euros. This also takes into account the coin's potential in the market and the interest it has shown in previous auctions.

Therefore, an estimated maximum purchase price could be 80 euros.