To estimate a maximum purchase price for the coin in question, we can analyze the provided data, taking into account the current condition of the coin (30 BC+) and the auction hammer prices from previous sales.

1. Condition: The coin has a condition of 30 (BC+), which indicates that it is not in very good shape. This generally negatively affects the hammer price.

2. Previous hammer prices: By observing the hammer prices of coins with higher conditions (70 and 95), we can see that the hammer prices have varied considerably. For example:
- A coin with a condition of 70 was auctioned for 200, 220, 175, and 180 euros.
- A coin with a condition of 95 was auctioned for 340 and 400 euros.

3. Average hammer price: The average hammer price for this coin in the past has been 211.92 euros, which can serve as a reference.

4. Starting price: The current starting price is 180 euros, indicating that the seller has expectations of a reasonable hammer price.

Given that the condition of the coin is quite low (30), it is likely that the hammer price will not reach the levels of coins in better condition. However, considering the average hammer price and the hammer prices of coins with similar conditions, an estimated maximum purchase price could be around 120-150 euros.

Therefore, an estimated maximum purchase price for this coin could be 150 euros.