The following solution is based on the idea of dynamic hedging. It is possible only because we can derive the fair price of your business even if it has uncertain outcome. We first need to find a risk-neutral world and then the fair price can be computed for any risky asset.
Assume F(x, y) is the fair price of your business after A wins x matches and B wins y matches. P(x, y) is the risk-neutral probability that A will win the final given the previous outcome. We have: F(x, y) = $2m * P(x, y), which can be recursively computed from the end.
At that time, if A wins one more match, the fair price will become F(x + 1, y). So to hedge the risk, you should bet on team B for: F(x + 1, y) - F(x, y)
If we apply this to the simpler case of whoever winning THREE matches first becomes the champion, the bet afer B wins the first match is: F(1, 1) - F(0, 1) = $1m - $2m * 5 / 16 = $375K (NOTE: assume whoever wins THREE matches first becomes the champion. NOT the real NBA rule.)