Based on the provided data, we can observe that the coin in question had a starting price of 30 euros in the most recent auction, with an estimated value of 50 euros and a final price of 30 euros. The coin's condition is described as 30 (BC+).

Historically, the coin has had starting prices ranging from 20 euros to 450 euros, with estimated values ranging from 50 euros to 600 euros. The final price has fluctuated between 30 euros and 700 euros in previous auctions.

Given that the coin will be auctioned soon and considering the historical data as well as the current condition of the coin, we could estimate a maximum purchase price around 60-70 euros. It is important to note that the most recent final price was 30 euros, so it is advisable not to exceed this value too much in the estimation of the maximum purchase price.