Based on the data provided, we can observe that the coin in question has had an average auction closing price of 133.02 euros in previous auctions. Additionally, the condition of this coin is rated at 70 (MBC-).

Considering that the starting price in the upcoming auction is 90 euros and that the estimated closing price has ranged between 120 and 200 euros in previous auctions, we could estimate a maximum purchase price of around 200 euros, taking into account the price history and the condition of the coin.

Therefore, an estimated maximum purchase price for this coin in the upcoming auction could be around 200 euros.