Based on the data provided, we can observe that the coin has had an average auction closing price of 184.67 euros in previous auctions. Additionally, the condition of this coin is rated at 30 (BC+).

Considering that the starting price for the upcoming auction is 15 euros and that the estimated closing price has ranged between 20 and 750 euros in previous auctions, we can estimate a maximum purchase price for this coin at around 200-250 euros, taking into account its condition and historical closing prices.

It is important to note that the final auction price may vary depending on the demand at that specific moment, so it is advisable to pay attention to the auction in order to adjust the offer accordingly.