  We study the power of price discrimination via an intermediary in bilateral
trade, when there is a revenue-maximizing seller selling an item to a buyer
with a private value drawn from a prior. Between the seller and the buyer,
there is an intermediary that can segment the market by releasing information
about the true values to the seller. This is termed signaling, and enables the
seller to price discriminate. In this setting, Bergemann et al. showed the
existence of a signaling scheme that simultaneously raises the optimal consumer
surplus, guarantees the item always sells, and ensures the seller's revenue
does not increase.
  Our work extends the positive result of Bergemann et al. to settings where
the type space is larger, and where optimal auction is randomized, possibly
over a menu that can be exponentially large. In particular, we consider two
settings motivated by budgets: The first is when there is a publicly known
budget constraint on the price the seller can charge and the second is the
FedEx problem where the buyer has a private deadline or service level
(equivalently, a private budget that is guaranteed to never bind). For both
settings, we present a novel signaling scheme and its analysis via a continuous
construction process that recreates the optimal consumer surplus guarantee of
Bergemann et al.
  The settings we consider are special cases of the more general problem where
the buyer has a private budget constraint in addition to a private value. We
finally show that our positive results do not extend to this more general
setting. Here, we show that any efficient signaling scheme necessarily
transfers almost all the surplus to the seller instead of the buyer.
