I recently consulted a friend on this topic.

He knew he wanted a nexus 6.

Choices were (ballpark numbers):
1. 5000 for the phone outright
2. 4000 for the phone with two year contract

I pressed him about option 2 (e.g. what are the consequences of breaking the contract?). He told me that doing so could put his hkid in bad standing, but he could get off the hook by reselling the contract).

I advised him to go with option 1 because his hkid is worth much more than 1000.