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

1. Current Condition: The coin has a condition of 30 (BC+), which indicates that it is not in very good shape. This generally reduces its value compared to coins in better condition.

2. Historical Prices: By looking at previous auction prices, we can see that coins of this reference have had a fairly wide price range. For example:
- In 2022, a coin with a condition of 80 was auctioned for 400 euros.
- In 2021, a coin with a condition of 30 was auctioned for 150 euros.
- In 2020, a coin with a condition of 70 was auctioned for 130 euros.

3. Starting Price and Average Hammer Price: The current starting price is 125 euros, and the average hammer price in the past has been 267.48 euros. This suggests that there is potential for an increase in the hammer price.

4. Recent Trends: Recent auctions have shown high hammer prices, even for coins with similar conditions.

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 200 euros. This is based on the fact that, although the condition is not optimal, the interest in the coin and previous hammer prices suggest that it could reach a reasonable price at auction.

Therefore, an estimated maximum purchase price could be 200 euros.