To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current Grade: The coin has a grade of 75 (MS), indicating a medium-good quality. This is relevant because coins in better condition tend to reach higher prices.

2. Previous Auction Prices: By observing previous auction prices for coins with similar grades (75 and 70), we can see that auction prices have varied, but generally, coins with a grade of 75 have reached auction prices ranging between 130 and 190 euros.

3. Average Auction Price: The average auction price for this coin is 146.48 euros, which gives us a good reference for what buyers are willing to pay.

4. Starting Price and Estimated Price: The starting price is 90 euros, and the estimated price is 150 euros. This suggests that there are expectations for the coin to sell for a price higher than the starting price.

5. Auction Trends: The coin has been auctioned 32 times, of which 30 have been sold. This indicates a consistent interest in the coin, which may influence the price.

Based on these factors, an estimated maximum purchase price could be in the range of 160 to 200 euros, considering that the highest auction price for similar grades has been 190 euros and that the average auction price is 146.48 euros.

Therefore, a reasonable maximum purchase price could be 180 euros. This allows for a margin for competition in the auction and aligns with previous auction prices.