Are 401(k)s Cheaper than Defined Benefit Pensions for Employers?

A NYT article discussing Republican plans to sharply limit the tax deduction for 401(k)s noted how these retirement accounts have largely replaced traditional defined benefit pensions and said that they were cheaper for employers. This is not entirely clear.

In principle a payment for a retirement benefit is supposed to be a substitute for wages. If a worker gets $2,000 a year paid into a defined benefit pension or a 401(k) plan, this is supposed to be offset by roughly a $2,000 reduction in...