Older workers are a bargain

1. More engaged and motivated. 2. Don't cost much more. 

An AARP study (of course, consider the source), shows this:

Cost: The incremental cost of getting and keeping more 50+ workers is about 1-2 percent in four key industries: engineering, financial services, health care and retail. Pay scales have moved from tenure-based to performance-based. Retirement plans have shifted from defined benefits to defined compensation. Health care insurance rate increases have slowed. Older workers are less likely to leave, which saves hiring and training costs.

Engagement: Sixty-five percent of 55+ workers are "engaged," compared to 58-60 percent of younger workers. Not a huge difference, but the study says a 5 percent difference yields a 3 percent increase in revenue growth.

[AARP: A Business Case for Workers Age 50+]