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 of 80 (MS+). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Prices: By observing previous auction prices for coins with similar conditions, we can see that:
- In 2018, a coin with a condition of 80 was auctioned for 90 euros.
- In 2022, another coin with a condition of 80 was auctioned for 260 euros, indicating a wide range depending on demand and other factors.

3. Average Auction Price: The average auction price for this coin is 136.97 euros, suggesting that, in general, coins of this reference tend to sell for a price higher than the starting bid.

4. Starting Price: The starting price is 80 euros, which may indicate a base price, but not necessarily the final auction price.

5. Auction Trends: The coin has been auctioned 35 times, of which 30 have sold. This indicates good demand and sustained interest in the coin.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is good and there are precedents of higher auction prices in the past. However, since the average auction price is 136.97 euros, a more conservative maximum purchase price could be around 170 euros.

Therefore, a reasonable estimated maximum purchase price would be 170 euros.