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

1. Current Condition: The coin has a condition rating of 30 (BC+), indicating that it is not in the best condition, but it is also not among the worst.

2. Auction History:
- The average hammer price in previous auctions is 33.3 euros.
- The coin has been auctioned 33 times, of which it has sold 23 times, indicating a reasonable sell-through rate.
- Previous hammer prices for coins with similar conditions (around 30) have varied, but there are examples of auctions reaching up to 50 euros in more favorable conditions.

3. Starting Price and Estimates:
- The current starting price is 25 euros, which is a good starting point.
- The average starting price in previous auctions is 29.18 euros, suggesting that the market is willing to pay a bit more than the starting price.

4. Recent Trends: In the most recent auctions, hammer prices have ranged between 25 and 50 euros, depending on condition and demand.

Based on these factors, an estimated maximum purchase price could be around 40-45 euros. This is based on the historical hammer prices for coins of similar condition and market interest. However, given that the condition of this coin is 30, it is wise not to exceed 45 euros to avoid overpaying.