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 70 (MS-), indicating that it is in an acceptable state, but not of the highest quality.

2. Auction History:
- The average hammer price for coins of similar condition (70) has been approximately 30-35 euros in previous auctions.
- In past auctions, hammer prices for coins with a condition of 70 have ranged between 20 and 40 euros.

3. Starting Price and Average Hammer Price:
- The current starting price is 30 euros, and the average hammer price is 50.16 euros, suggesting that there is potential for the coin to sell at a higher price.

4. Recent Trends: In the most recent auctions, the hammer price has been 30 euros for coins with similar condition, indicating that the market is stable.

5. Sale Expectations: Given that there is an auction scheduled in the coming days, and considering that there have been 42 previous auctions with 25 sales, there is moderate interest in this coin.

Based on these factors, an estimated maximum purchase price could be between 40 and 50 euros. This is because, although the condition is not the highest, the price history and interest in the coin suggest that it could reach a higher price at auction.

Therefore, a reasonable maximum purchase price could be 45 euros.