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

1. Current Condition: The coin has a condition of 90 (EF), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Previous Auction Prices: By looking at previous auction prices for coins with a similar condition (90 or 95), we can see that prices have varied. For example, in recent auctions, coins with a condition of 90 have reached hammer prices of up to 100 euros.

3. Average Hammer Price: The average hammer price for this coin is 47.27 euros, suggesting that, in general, buyers are willing to pay around this amount.

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

5. Starting Price: The starting price is 30 euros, which is relatively low compared to previous hammer prices.

Taking all these factors into account, an estimated maximum purchase price for the coin could be between 80 and 120 euros, considering that the condition is good and there is an upward trend in hammer prices. A price of 100 euros could be a reasonable target, as it aligns with the hammer prices of coins in similar condition in the past.