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

1. Current starting price: 1000 euros.
2. Current grade: 80 (MBC+).
3. Auction history: The coin has been auctioned 11 times and has sold on all occasions, indicating good demand.
4. Average hammer price: 1190 euros, suggesting that, on average, similar coins sell for a price higher than the starting price.
5. Previous prices:
- In previous auctions, hammer prices have varied, but there are examples where the coin sold for 1150 euros (2020) and 1200 euros (2017).
- In the most recent auction (2022), the hammer price was 1400 euros, indicating that demand may be increasing.

Given that the coin's grade is 80 (MBC+), which is a good grade, and considering the hammer price history, an estimated maximum purchase price could be set in a range between the average hammer price and a bit more, given the interest in the coin.

Estimated maximum purchase price:
We could consider a maximum purchase price of approximately 1350 euros. This price reflects an increase over the average hammer price, taking into account the good condition and the price trend in recent auctions.