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

1. Current Condition: The coin has a condition rating of 80 (MBC+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for similar coins in the past is 346.66 euros.
- Coins with similar conditions (85 and 90) have reached hammer prices of up to 495 euros (in the case of condition 95) and 230 euros (in the case of condition 90).
- The last auction of a coin with condition 95 reached a hammer price of 1500 euros, indicating that there is an active market willing to pay high prices for coins in good condition.

3. Starting Price and Average Starting Price:
- The current starting price is 30 euros, which is significantly lower than the average starting price of 154.54 euros. This suggests that there is potential for an increase in the hammer price.

4. Recent Trends:
- In recent auctions, hammer prices have shown a trend of being higher, especially for coins in similar conditions.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 300 to 400 euros, considering that the condition is good and that the auction history shows hammer prices that justify this estimate.

Therefore, a reasonable maximum purchase price could be 350 euros.