Using a game-theoretical approach, this paper develops a duopoly model and examines value-added service (VAS) investments and pricing strategies on video platforms with opposite inter-group network externalities between two groups. We consider two scenarios with VAS investment, namely, a single platform investing in VASs for advertisers (S-Model) and both platforms investing in VASs for advertisers (B-Model). We found the following: (i) In the S-Model, the investing platform’s VAS level remains maximum when the marginal investing cost is low; otherwise, it decreases with the cost. Investing and non-investing platforms’ advertising prices are unaffected by the marginal investing cost if the cost is low; otherwise, the prices decrease and increase with the cost, respectively. Furthermore, the investing platform’s advertising price is higher than the non-investing platform’s. (ii) In the B-Model, the two platforms’ VAS levels remain maximum if the marginal investing cost is low; otherwise, they decrease with the cost. The two platforms’ advertising prices are equal and irrelevant to the marginal investing cost. (iii) The investing platform’s VAS level in the S-Model is higher than or the same as that in the B-Model and the investing platform’s advertising price in the S-Model is higher than that in the B-Model. (iv) Compared to the scenario without VAS investment, the investing platform’s advertising price is higher in the S-Model, but the same in the B-Model.