  We study the problem of pricing under a Multinomial Logit model where we
incorporate network effects over the consumer's decisions. We analyse both
cases, when sellers compete or collaborate. In particular, we pay special
attention to the overall expected revenue and how the behaviour of the no
purchase option is affected under variations of a network effect parameter.
Where for example we prove that the market share for the no purchase option, is
decreasing in terms of the value of the network effect, meaning that stronger
communication among costumers increases the expected amount of sales. We also
analyse how the customer's utility is altered when network effects are
incorporated into the market, comparing the cases where both competitive and
monopolistic prices are displayed. We use tools from stochastic approximation
algorithms to prove that the probability of purchasing the available products
converges to a unique stationary distribution. We model that the sellers can
use this stationary distribution to establish their strategies. Finding that
under those settings, a pure Nash Equilibrium represents the pricing strategies
in the case of competition, and an optimal (that maximises the total revenue)
fixed price characterise the case of collaboration.
