For Israel, the costs would be more diplomatic: a deterioration of its relationship with Egypt, which is playing a crucial role in brokering the ceasefire, and a further lessening of its regional and international standing following the likely increase in civilian Palestinian casualties. What's more, if mismanaged, a ground invasion could actually weaken the popularity of Prime Minister Benjamin Netanyahu and his government, complicating their path to victory in Israel’s Jan. 22 elections.
Enforcing a ceasefire and avoiding an escalation is also important from a broader regional perspective. Between an ongoing bloody civil war in Syria, mass-scale anti-government demonstrations in Jordan, and brewing unrest in the West Bank, a military escalation between Israel and Hamas risks bringing further instability at the regional level – and distracting regional and international actors from these other crises.
A ceasefire seems specifically in the direct interests of a number of regional stakeholders, led by Qatar and Egypt.
In the past year, Hamas has repositioned itself and reviewed its regional alliances as a result of the so-called Arab Awakening. In particular, a strong disagreement between Hamas and its historical patron, the Assad regime, over the way the Syrian government was handling the political opposition has led to the relocation of the group's political bureau away from Damascus.