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 in previous auctions is 337.14 euros.
- The last auction with a similar condition (70) had a hammer price of 360 euros.
- In previous auctions, hammer prices have varied, but they have reached up to 420 euros in a recent auction with better condition (90).

3. Starting Price and Average Starting Price: The current starting price is 300 euros, and the average starting price in the past has been 270 euros. This suggests that the current starting price is reasonable and could attract bidders.

4. Sales Trends: The coin has been sold in 7 out of the last 9 auctions, indicating a consistent interest in the coin.

Based on these factors, an estimated maximum purchase price could be in the range of 360 to 420 euros, considering that the current condition is 70 and there is demonstrated interest in the coin.

Therefore, an estimated maximum purchase price could be 400 euros. This allows for a margin for competition in the auction, given the price history and the condition of the coin.