Question: It became virtually impossible for Cubans to live on rations alone.
Cubans live on rations.

Answer: yes

Question: For a number of years, some mailers have pursued the idea of establishing customized postal rates and/or terms of service through negotiation with the Postal Service.
Some mailers would like to have customized rates and terms of service.

Answer: yes

Question: Each party receives and sacrifices something of value.
Objects of worth are both received and sacrificed by each party.

Answer:
yes