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

1. Condition: The coin has a condition of 70, which is considered "MBC-". This indicates that the coin is in an acceptable state, but not of high quality. In the past, coins with a similar condition have had varying auction prices.

2. Previous auction prices:
- In previous auctions, coins with a condition of 70 have had auction prices of 30 (2020-11-19), 14 (2020-05-26), and 26 (2023-01-18).
- The trend shows that the auction price may be in a range of 14 to 30 euros for coins with similar condition.

3. Average auction price: The average auction price for this coin is 30.25 euros, suggesting that, in general, buyers are willing to pay around this amount.

4. Starting price: The starting price is 10 euros, which is relatively low compared to previous auction prices.

5. Estimation: Given that the condition is 70 and considering previous auction prices, an estimated maximum purchase price could be situated in the upper range of previous auction prices.

Taking all these factors into account, an estimated maximum purchase price for this coin could be 30 euros. This is based on the highest auction price recorded for a coin with a similar condition.