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

1. Current starting price: 130 euros.
2. Coin condition: 70 (MBC-), which indicates an acceptable but not excellent condition.
3. Auction history:
- In 2018, the coin was auctioned with a starting price of 90 euros and sold for 220 euros.
- In 2022, the starting price was the same (90 euros), with a final bid of 260 euros.

4. Average final bid price: 240 euros, indicating that, in general, coins of this reference tend to sell for a price higher than the starting price.

Given that the coin has a starting price of 130 euros and considering that in the past it has reached final bid prices of up to 260 euros, we can make an estimation.

Estimation of the maximum purchase price:
- Since the highest final bid in the past was 260 euros and considering that the condition is the same (70), a reasonable maximum purchase price could be in the range of 240 to 260 euros, as the current starting price is higher than in previous auctions.

Therefore, an estimated maximum purchase price could be 250 euros. This allows for a margin for competition in the auction, taking into account the price history and the condition of the coin.