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

1. Current Condition: The coin has a condition rating of 80 (MS+), indicating that it is in relatively good shape. This suggests that its value should be above that of coins in worse conditions.

2. Historical Prices: By looking at previous auction prices for coins with a similar condition (80), we can see that they have reached hammer prices of up to 220 euros in recent auctions.

3. Average Hammer Price: The average hammer price for this coin is 94.21 euros, which is also a good indicator of the expected value.

4. Starting Price: The current starting price is 30 euros, which is quite low compared to previous hammer prices.

5. Sales Trends: The coin has been sold in 28 out of 35 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 250 euros, considering that the condition is good and there are precedents for higher hammer prices in the past. A more conservative price could be around 200 euros, given that it is a value seen in recent auctions for coins in similar conditions.