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

1. Current Condition: The coin has a condition rating of 70 (MS-), which is a medium level. This suggests that its value will not be as high as that of coins in better condition.

2. Auction History:
- The average hammer price for coins of similar condition (70) in the past has been approximately 173.71 euros.
- In previous auctions, hammer prices for coins with a condition of 70 have varied, but they have sold for prices ranging between 120 and 237 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 150 euros, which is slightly higher than the average starting price of 126.09 euros. This may indicate that the seller has higher expectations due to demand or the quality of the coin.

4. Recent Trends: In the most recent auctions, the hammer price has been around 190-210 euros for coins of similar condition.

Based on these factors, an estimated maximum purchase price could be in the range of 200 to 230 euros, considering that the market may be willing to pay a bit more for a coin in good condition that has a history of successful sales.

Therefore, a reasonable maximum purchase price could be 220 euros.