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 70 (VF-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for coins with a similar condition (70) has been approximately 55-70 euros in recent auctions.
- In the past, coins with a condition of 70 have reached hammer prices of up to 55 euros (as seen in the auction on 2018-12-11).

3. Starting Price and Average Hammer Price:
- The current starting price is 30 euros, which is relatively low compared to the average hammer price of 89.03 euros.
- The average starting price of 47.88 euros also suggests that there is potential for an increase in the hammer price.

4. Recent Trends:
- In recent auctions, the hammer price has shown a trend of being higher than the starting price, indicating growing interest in this coin.

Based on these factors, an estimated maximum purchase price for the coin could be between 70 and 90 euros, considering that the interest in the coin and its condition are favorable. However, since the starting price is 30 euros, it may be possible to acquire it for a lower price, but the mentioned range is a good target for a competitive bid.