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. This will affect its value compared to coins in better condition.

2. Auction History:
- The average hammer price for similar coins in the past has been 373.68 euros.
- Previous auctions of this coin have shown hammer prices that vary significantly, with some reaching up to 1600 euros in much better conditions (condition rating of 90).
- Most recent auctions of coins with similar conditions have had hammer prices ranging between 110 and 400 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 25 euros, which is quite low compared to the average starting price of 176.21 euros.

4. Recent Trends: In the most recent auctions, hammer prices for coins with similar conditions have been in the range of 110 to 200 euros.

Given all this, and considering that the condition of the coin is a limiting factor, an estimated maximum purchase price could be in the range of 150 to 250 euros. This is based on the historical hammer prices for coins of similar condition and the current market context.

Therefore, a reasonable maximum purchase price could be 200 euros.