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

1. Current Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Previous Auction Prices:
- The average hammer price from previous auctions is 222.33 euros.
- The most recent auction (2023) had a hammer price of 460 euros for a coin with a condition rating of 95, indicating that coins in better condition can reach significantly higher prices.
- The 2021 auction with a condition rating of 95 had a hammer price of 370 euros, which also suggests that condition strongly impacts the price.

3. Starting Price and Average Starting Price:
- The current starting price is 130 euros, which is below the average starting price of 132.5 euros. This could indicate potential for an increase in the hammer price.

4. Sales Trends: The coin has sold every time it has been auctioned, suggesting consistent demand.

5. Condition-Based Estimation: Given that the coin's condition is 80, we can estimate that its hammer price could be in a range lower than that of coins with a condition of 95, but higher than that of coins with a condition of 70.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 250 to 300 euros, considering that the condition is good and that interest in the coin appears to be high.

Therefore, a reasonable maximum purchase price could be 300 euros.