It takes about 4 year of utilization to recover the cost of fitting winglets. On young airframes this is a feasible proposition as there is also "added value" to the airframe when it is time to dispose of it through resale. On high cycle airframes the benefit is unlikely to be recovered.
Boeing (even before discounts) pitched the retail price of the 787-8 at the high end of the same price band for a 767-300. This made it very attractive and undoubtably was a major factor in the record pre-roll out sales numbers achieved. Boeing was a victim of their own optimism. They priced the construction costs on their belief that pre-assembled sections would (cost effectively) be delivered from risk bearing global partners, and be "stiched together" in just a few days in Seattle.
That optimism has fallen off a well publicised cliff! Cost overruns are rumoured (reliably) to be in the tens of billions of dollars. This means that a lot of units have been pre-sold at bargain basement prices. Notwithstanding the contractual compensation payments, Boeing would undoubtably be happy to see some of these "loss leader" orders evaporate, so that it can sell them at more realistic prices. However the customer airlines are not stupid either, and are unlikely to let them off the hook so easily.
For that reason alone, Boeing has no reason to offer "sweetners" beyond the contractual arrangements already in place.