A perfectly horrible phrase used in American business
that literally indicates whether one has made a profit,
taken a loss, or simply broken even. It
comes from the world of accounting: when you add up all
the debits and credits, payables and receivables, the
last line of the ledger has the big number everyone
wants to hear.
Figuratively it is used as a synonym for net effect,
especially in an economic sense.
The question, "So what's the bottom line?" although
incorrect in its expression, is taken to mean "What
will this cost me?"
The phrase protecting the bottom line means
cutting what are seen as unnecessary expenditures
(this could include laying off personnel) in order
to make a company's ledger look more profitable.
It is usually an accounting, not a budgetary issue;
that is to say, more of appearance than reality.