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+), indicating that it is in relatively good shape. This suggests that its value could be in the upper range of previous auctions.

2. Previous Auction Prices: Looking at previous auction prices, we can see that in past auctions, coins with similar conditions have reached hammer prices of up to 650 euros (in the case of the 2018 auction). However, there are also lower hammer prices, such as 47 euros in 2016.

3. Average Hammer Price: The average hammer price for this coin is 180.13 euros, which provides a good reference point.

4. Recent Trends: In the most recent auctions, hammer prices have shown a trend of being higher, such as the hammer price of 199 euros in 2023.

5. Starting Price and Previous Sales: The current starting price is 70 euros, and there have been 8 sales in the past, indicating that there is interest in the coin.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 200 to 250 euros. This is based on the current condition, previous hammer prices, and the price trend in recent auctions.

Therefore, a reasonable maximum purchase price could be 250 euros.