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

2. Previous Auction Prices: By looking at previous auction prices for coins with similar conditions (around 80), we can see that they have reached auction prices that vary, but some examples are:
- 2022-10-19: Auction price of 160 (condition 70)
- 2023-05-24: Auction price of 420 (condition 85)
- 2024-02-14: Auction price of 300 (condition 80)

3. Average Auction Price: The average auction price for this coin is 257.93 euros, which gives us a good reference for what buyers are willing to pay.

4. Recent Trends: In the most recent auctions, the auction prices have shown an increase, which could indicate a rising trend in interest for this coin.

5. Starting Price: The starting price is 125 euros, suggesting that the seller expects a reasonable price, but the auction price could be significantly higher.

Based on these factors, an estimated maximum purchase price could be in the range of 300 to 400 euros, considering that the condition is good and there is growing interest in this coin. This aligns with previous auction prices and the average auction price.

Therefore, an estimated maximum purchase price could be 350 euros.