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 75 (VF), indicating that it is in an acceptable state, but not among the best conditions. This may affect its value compared to coins in better condition.

2. Auction History:
- The coin has been auctioned 8 times in the past, of which it has sold 5 times. This indicates moderate interest in the coin.
- Previous hammer prices varied, but there are examples of hammer prices reaching up to 1100 euros for coins in condition 90, and lower prices for coins in condition 75.

3. Starting Price and Average Prices:
- The current starting price is 90 euros, which is relatively low compared to the average starting price of 279.87 euros and the average hammer price of 466.82 euros.
- This suggests that there is potential for the hammer price to be significantly higher than the starting price.

4. Price Trends:
- In previous auctions, coins with similar condition (75) have had hammer prices ranging from 50.95 to 101.9 euros, indicating that the hammer price may be in a lower range compared to coins in better condition.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 250 euros. This is based on the fact that, although the condition is not the best, the interest in the coin and the price history suggest that it could reach a reasonable price at auction.

Therefore, a reasonable maximum purchase price could be 200 euros.