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 price of 50 euros and a final price of 45 euros. Additionally, its condition has been assessed at 70 (MBC-).

Considering the previous prices of this coin, as well as its condition and the fact that it has been auctioned 26 times in the past, we can estimate a maximum purchase price for this coin in the upcoming auction. Since the most recent final price was 45 euros and there have been auctions where the estimated price reached up to 100 euros, we could consider a maximum purchase price range between 50 and 100 euros.

Given that the condition of the coin is 70 (MBC-), indicating it is not in the best condition, we could lean towards the lower end of this range, so an estimated maximum purchase price for this coin in the next auction could be around 50-60 euros.