Based on the data provided, we can observe that the coin has had an average auction price of 311.91 euros in the past. Additionally, it has been auctioned 55 times and sold in 45 of those auctions.

The current condition of the coin is 30 (BC+), indicating that it is not in the best condition, but it is not in the worst either.

Some previous prices of the coin have ranged between 25 euros and 1800 euros, depending on the auction and the condition of the coin.

Given that the coin will be auctioned in the upcoming days with a starting price of 30 euros, and considering its auction price history, we could estimate a maximum purchase price around 350 euros. This estimation is based on the fact that the average auction price has been 311.91 euros and taking into account that the coin has sold in most of the previous auctions.

It is important to note that the final auction price may vary depending on the demand at that specific moment, but 350 euros could be a good reference point as an estimated maximum purchase price.