To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Starting Price: 1000 euros. This is the initial price set for the auction.
2. Condition: The coin has a condition rating of 70 (VF-), indicating that it is in an acceptable state, but not of high quality. This may influence the final price.
3. Auction History: The coin has been auctioned in the past on two occasions, with a hammer price of 380 euros in one of them. This suggests that the market has valued the coin in a lower range than the current starting price.
4. Average Hammer Price: The average hammer price of 380 euros also indicates that, in general, buyers are not willing to pay much more than this amount for the coin.
5. Average Starting Price: The average starting price of 533.33 euros may be an indicator of what sellers have expected to obtain in the past.

Given that the current starting price is significantly higher than previous hammer prices and the average hammer price, it is likely that buyer interest will be limited.

Taking all these factors into account, an estimated maximum purchase price could be around 400-500 euros, which is a range more in line with the sales history and the condition of the coin. This would allow a buyer to align with the market value observed in previous auctions.