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 75 (MBC), indicating an average quality. This is important because coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for coins with a similar condition (75) in the past has been approximately 258.45 euros.
- In recent auctions, coins with a condition of 75 have sold for prices ranging from 290 to 460 euros.

3. Starting Price: The starting price of 350 euros is an indicator of what is expected to be obtained in the auction. However, the starting price does not always translate into the final hammer price.

4. Sales Trends: The coin has been auctioned 30 times, of which 29 have sold. This suggests high demand and good interest in the coin, which can influence the final price.

5. Comparison with Previous Prices: In previous auctions, coins with similar conditions have reached hammer prices that exceed the current starting price. For example, in a recent auction, a coin with a condition of 75 sold for 290 euros.

### Estimation of Maximum Purchase Price
Considering all these factors, an estimated maximum purchase price could be between 400 and 460 euros. This is based on the fact that the starting price is 350 euros and that in previous auctions, coins with a similar condition have reached higher hammer prices.

Therefore, a reasonable maximum purchase price could be 450 euros. This allows for a margin for competition in the auction, given the demonstrated interest in coins of this condition.