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 with similar conditions (although some are better) have had varying hammer prices. For example:
- In 2022, a coin with a condition of 30 was auctioned for 60 euros.
- In other auctions, coins with conditions of 70 and 80 have reached hammer prices of up to 190 euros.

3. Average Hammer Price: The average hammer price for this coin is 92.97 euros, but this includes coins in better condition.

4. Starting Price: The starting price is 50 euros, which can be a good indicator of the seller's expectations.

5. Sales Trends: The coin has been auctioned 41 times, of which 35 have sold. This indicates good demand, although the hammer price can vary.

Given that the condition of the coin is relatively low (30), and considering previous hammer prices and the starting price, an estimated maximum purchase price could be between 50 and 70 euros. This is based on the fact that, although there are coins in better condition that have reached higher prices, the current condition of this coin will limit its value.

Therefore, an estimated maximum purchase price could be 70 euros.