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 indicates that it is in relatively good shape, but not of the best quality (FDC).

2. Previous Prices: Looking at previous auction prices for coins with similar conditions (70 and 75), we can see that:
- In past auctions, coins with a condition of 70 have reached hammer prices of up to 140 euros.
- Coins with a condition of 75 have reached hammer prices of up to 110 euros.

3. Average Hammer Price: The average hammer price for this coin is 184.55 euros, suggesting that, in general, coins of this reference tend to sell for higher prices.

4. Starting Price and Average Starting Price: The current starting price is 30 euros, and the average starting price is 59.78 euros. This indicates that the starting price is relatively low compared to previous hammer prices.

5. Auction Trends: Since the coin has been auctioned 23 times and all have been sold, this suggests a consistent demand.

Based on these factors, an estimated maximum purchase price could be in the range of 140 to 200 euros, considering that the condition is 70 and there are precedents for higher hammer prices. However, given that the starting price is 30 euros, it might be reasonable to set a maximum purchase price around 150-180 euros, depending on the competition in the auction and the interest of other bidders.

Therefore, an estimated maximum purchase price could be 180 euros.