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

1. Current starting price: 200 euros.
2. Current condition: 80 (MBC+), which is good condition.
3. Auction history:
- In the March 2022 auction, the coin was offered at a starting price of 230 euros and sold for 360 euros.
- In the January 2023 auction, the starting price was 250 euros and it sold for 320 euros.

4. Average starting and final prices:
- Average starting price: 226.67 euros.
- Average final price: 340 euros.

5. Price trends: The coin has shown an increase in final prices at previous auctions, suggesting there is growing interest.

Given that the current condition of the coin is better than in the January 2023 auction (where the condition was 70), and considering that the final price has been above 300 euros on both occasions, we can estimate a maximum purchase price.

Estimation of the maximum purchase price:
- Based on the average final price (340 euros) and the fact that the condition is good, a reasonable maximum purchase price could be in the range of 350 to 400 euros.

Therefore, an estimated maximum purchase price for this coin could be approximately 370 euros.