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 (MS-). 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 327.69 euros.
- The last auction with a hammer price was 400 euros for a coin with a condition of 70.
- In previous auctions, hammer prices have varied, but there are examples of sales that reached up to 600 euros for coins in better condition.

3. Starting Price and Estimated Price:
- The current starting price is 300 euros, which serves as a benchmark for the beginning of the auction.
- The estimated price in previous auctions has been up to 500 euros, indicating potential for a higher hammer price.

4. Sales Trends: The coin has been sold in 14 out of 16 auctions, suggesting there is consistent interest in this coin.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 500 euros, considering that the condition is a limiting factor and that interest in the coin appears to be solid. Therefore, a reasonable maximum purchase price could be 450 euros.