Given that the coin has a condition of 30 (BC+), which indicates that it is in relatively low condition, and considering that there have been no previous auctions or sales of this reference, the estimated maximum purchase price could be slightly higher than the starting price, but not by much, as the lack of sales history may make buyers cautious.

Since the starting price is 30 euros and there is no historical data suggesting a significant increase in value, an estimated maximum purchase price could range between 30 and 50 euros, depending on collectors' interest in the auction. However, a more conservative price could be around 40 euros, considering the condition and the lack of history.