To estimate a maximum purchase price for the coin in question, we can analyze the provided data, taking into account the current condition of the coin (70, VF-) and previous auction prices.

1. Condition: The coin has a condition of 70, which is considered VF-. In the past, coins with a similar condition have had auction prices that vary, but we can observe that the highest auction price for a similar condition was 70 euros in 2020.

2. Previous auction prices:
- In 2019, a coin with a condition of 70 was auctioned for 45 euros.
- In 2018, a coin with a condition of 75 was auctioned for 30 euros.
- In 2022, a coin with a condition of 70 was auctioned for 30 euros.

3. Price trends: The average auction price for similar coins seems to be in a range of 30 to 70 euros, depending on the condition and demand at the time of the auction.

4. Starting price and estimates: The current starting price is 9 euros, and the average auction price in the past has been 28.8 euros. This suggests that interest in the coin may be moderate, but the auction price could be significantly higher than the starting price.

5. Final estimate: Given that the condition is 70 and considering previous auction prices, an estimated maximum purchase price could be around 50-60 euros. This is based on the highest auction price recorded for a similar condition and the general interest in the coin.

Therefore, an estimated maximum purchase price for this coin could be 60 euros.