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

1. Current Condition: The coin has a condition of 70 (VF-). This indicates that it is in an acceptable state, but not of high quality. In comparison with previously auctioned coins, those with a condition of 75 or 80 have reached higher auction prices.

2. Previous Auction Prices:
- In previous auctions, coins with a condition of 70 have had auction prices of up to 9 euros.
- Coins with a condition of 75 have reached auction prices of up to 50 euros.
- Coins with a condition of 80 have reached auction prices of up to 200 euros.

3. Average Auction Price: The average auction price for this coin is 44.85 euros, suggesting that, in general, coins of this reference tend to sell for relatively high prices.

4. Starting Price: The starting price is 15 euros, which is a good starting point for the auction.

5. Sales Trends: Out of the 17 times it has been auctioned, it has sold 13 times, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 30 to 50 euros, considering that the current condition is 70 and the average auction price is 44.85 euros.

Therefore, a reasonable estimated maximum purchase price could be 40 euros. This allows for a margin for competition in the auction, given that the starting price is 15 euros.