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

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. Starting Price: The starting price is 450 euros. This may indicate the seller's expectations, but not necessarily the actual value of the coin.

3. Sales History:
- The average hammer price in previous auctions is 330.49 euros.
- In past auctions, coins with similar conditions (around 80) have had hammer prices that varied, but some examples are:
- A coin with a condition of 80 was sold for 245 euros (2014).
- Another with a condition of 85 was sold for 391 euros (2023).
- A coin with a condition of 90 was sold for 440 euros (2023).

4. Recent Trends: In the most recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

5. Comparison with Previous Prices: The coin has had a maximum hammer price of 480 euros in the past, suggesting that there is a market willing to pay higher prices for quality coins.

Based on these factors, an estimated maximum purchase price for the coin could be between 400 and 480 euros, considering that the condition is good and there is market interest. However, since the starting price is 450 euros, a realistic hammer price could be closer to 400-450 euros, depending on the competition in the auction.

Therefore, an estimated maximum purchase price could be approximately 480 euros.