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

1. Current Condition: The coin has a condition of 70 (MBC-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Auction Prices: By observing previous auction prices for coins with similar conditions, we can see that:
- Coins with a condition of 75 have reached auction prices of up to 1,100 euros.
- Coins with a condition of 85 have reached auction prices of up to 1,310 euros.
- Coins with a condition of 90 have reached auction prices of up to 1,153 euros.

3. Average Auction Price: The average auction price for this coin is 874.66 euros, which gives us an idea of the general market value.

4. Starting Price: The starting price is 200 euros, indicating that the auctioneer expects a low initial price compared to previous auction prices.

5. Recent Trends: In the most recent auctions, the auction prices have varied, but they have remained in a range that suggests demand for this coin is still strong.

Based on these factors, an estimated maximum purchase price for the coin with a condition of 70 could be in the range of 600 to 800 euros. This is based on the fact that, although the condition is not the highest, there is a history of auction prices suggesting it could reach a significant value at auction.

Therefore, a reasonable maximum purchase price could be 800 euros.