To estimate a maximum purchase price for the coin in question, we can analyze 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 for coins with a similar condition (70) has been approximately 193.56 euros.
- In previous auctions, hammer prices for coins with a condition of 70 have varied, reaching up to 260 euros in some cases.

3. Starting Price: The current starting price is 150 euros, which is below the observed average hammer price.

4. Recent Trends: In the most recent auctions, hammer prices for coins with a condition of 70 have been in a range of 170 to 220 euros.

5. Comparison with Previous Prices: In previous auctions, the highest hammer price for coins with a condition of 70 has been 260 euros, suggesting there is potential for price increase.

Based on these factors, an estimated maximum purchase price could be in the range of 220 to 260 euros, considering that the condition is a key factor and that the hammer price has shown a trend of increasing in recent auctions.

Therefore, a reasonable estimated maximum purchase price could be 250 euros.