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 75 (MBC), which indicates that it is in an acceptable state, but not of the highest quality.

2. Previous Prices: By observing previous auction prices for coins with a similar condition (75-80), we can see that auction prices have varied. For example:
- In previous auctions, coins with a condition of 75 have reached hammer prices of 80 to 110 euros.
- Coins with a condition of 80 have reached hammer prices of up to 120 euros.

3. Average Hammer Price: The average hammer price for this coin is 178.66 euros, but this includes coins of different conditions. Given that the condition of this coin is 75, it is likely that the hammer price will be below this average.

4. Starting Price: The starting price is 100 euros, which may be a good indicator of the seller's expectations, but not necessarily of the final hammer price.

5. Auction Trends: The coin has been auctioned 97 times, with a high percentage of sales (89 out of 97). This suggests that there is consistent interest in this coin, which may influence the price.

Based on these factors, an estimated maximum purchase price for this coin could be between 100 and 130 euros, considering that the condition is a limiting factor and that interest in the coin may keep the price within a reasonable range.

Therefore, a reasonable maximum purchase price could be 130 euros.