In my opinion it's a mistake to come up with perks just so you can tell the right story. In his most recent book Clay Christensen describes what makes you love your job better than anything else I've read. He distinguishes between motivators and hygiene factors (mainly citing Frederick Herzberg's research): "Motivation factors include challenging work, recognition, responsibility, and personal growth. Motivation is much less about external prodding or stimulation, and much more about what’s inside of you and inside of your work." On the other hand he lists hygiene factors: "status, compensation, job security, work conditions, company policies, and supervisory practices." (from http://www.fastcompany.com/1836982/clayton-christensen-how-f... and his book). You can pile up perks as much as you want; they just serve as hygiene factors. As long as your motivators are not met, a high retention quote is wishful thinking. HR departments at bigger startups (and bigger perks) know that all too well.

At the end of the day you don't work for the big colorful slide at your office, or Whiskey Fridays, or your favorite 80's arcade video game. Cynically speaking, these are just there to make your long work days a bit sweeter.

So what's left for startups to retain their top employees? It's figuring out what truly motivates them. This takes a lot of hard work, empathy, and will. It's a long term investment. As such it might not pay off in the short term, but it might well give you in return the high retention rate you're looking for.