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 30 (BC+), indicating that it is not in very good shape. This will negatively affect its value compared to coins in better condition.

2. Current Listing Price and Historical Prices: The current listing price is 70 euros, which is significantly lower than the average listing price of 208.07 euros and the average hammer price of 342.18 euros. This suggests that the listing price is attractive and could draw in more bidders.

3. Sales History: The coin has been auctioned 77 times, of which 69 have been successful sales. This indicates good demand in the past. However, previous hammer prices have varied significantly, with some reaching up to 2000 euros in much better conditions.

4. Recent Trends: In the most recent auctions, hammer prices for coins with similar conditions (around 70-80) have been in the range of 200-400 euros.

5. Estimation Based on Historical Data: Given that the condition of this coin is 30, and considering that coins in similar conditions have reached hammer prices of up to 400 euros, a maximum estimated purchase price could be set in a more conservative range.

### Final Estimation
Taking all these factors into account, a maximum estimated purchase price for this coin could be 150-200 euros. This is based on the current condition and the fact that the listing price is relatively low, which could attract bidders.