Based on the data provided, we can observe that the coin in question has had an average auction closing price of 377.02 euros in previous auctions. Additionally, the current condition of the coin is graded at 30 (BC+).

Considering that the starting price for the upcoming auction is 175 euros and the estimated closing price is 1000 euros, we can see that there is an upward trend in the closing price of the coin.

Given that the current condition of the coin is 30 (BC+), and considering that the estimated closing price in previous auctions has ranged between 120 and 8000 euros, we could estimate a maximum purchase price around 900-1000 euros, taking into account the upward trend in closing prices and the condition of the coin.

It is important to note that the final closing price may vary depending on factors such as demand at the auction, competition from other bidders, and specific interest in the coin in question.