  We consider pricing in settings where a consumer discovers his value for a
good only as he uses it, and the value evolves with each use. We explore simple
and natural pricing strategies for a seller in this setting, under the
assumption that the seller knows the distribution from which the consumer's
initial value is drawn, as well as the stochastic process that governs the
evolution of the value with each use.
  We consider the differences between up-front or "buy-it-now" pricing (BIN),
and "pay-per-play" (PPP) pricing, where the consumer is charged per use. Our
results show that PPP pricing can be a very effective mechanism for price
discrimination, and thereby can increase seller revenue. But it can also be
advantageous to the buyers, as a way of mitigating risk. Indeed, this
mitigation of risk can yield a larger pool of buyers. We also show that the
practice of offering free trials is largely beneficial.
  We consider two different stochastic processes for how the buyer's value
evolves: In the first, the key random variable is how long the consumer remains
interested in the product. In the second process, the consumer's value evolves
according to a random walk or Brownian motion with reflection at 1, and
absorption at 0.
