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

1. Current Condition: The coin has a condition of 80 (MS+), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Auction Prices: By observing the previous auction prices of coins with similar conditions, we can see that:
- Coins with a condition of 75 have reached auction prices of up to 400 euros.
- Coins with a condition of 85 have reached auction prices of up to 650 euros.

3. Average Auction Price: The average auction price for this coin is 294.5 euros, which gives us a good reference for what buyers are willing to pay.

4. Starting Price and Average Starting Price: The current starting price is 175 euros, and the average starting price is 178.54 euros. This suggests that the market is willing to accept a starting price in that range.

5. Recent Trends: In the most recent auctions, the hammer prices have varied, but there are examples of coins with similar conditions that have reached hammer prices of 480 euros and more.

### Estimation of Maximum Purchase Price
Given that the coin has a condition of 80 (MS+) and considering the previous auction prices, a reasonable maximum purchase price could be in the range of 400 to 500 euros. This is based on the fact that coins with similar conditions have reached auction prices in that range, and since the condition of this coin is quite good, it is reasonable to expect that buyers would be willing to pay a price in that range.

Therefore, an estimated maximum purchase price could be approximately 450 euros.