This is fascinating to me because the days of plowing through leads with auto responders, progressive workflow templates with a single drop in, etc. are over in my humble opinion. Speaking both from someone that just was in the market for a new car (wife was) and someone that oversees between 500 and 1,000 mystery web shops monthly (ongoing retail and onetime wholesale initiatives) I can tell you there's such a disappointing difference between a truly engaged sales pro and an overwhelmed CRM checkbox clicking jockey....
Then there's the "experience" guys where everything "is what it is" and you do everything yourself. It sounds groovy to guys like us but the reality is the car buying public can't figure it out. I'm sure a test market in San Francisco and perhaps another one in New York City consisting of hipsters did well with it but that's not the entire audience nor is it even the majority of the intended audience of a dealer anywhere. These aren't shirts at Penny's but cars, the second largest purchase someone will make in their lifetime and some handholding needs to be done.
The stores that do have an appropriate staff to lead ratio which focuses on end user ease and experience simply make more deals, close at a higher rate and unlike the tech only companies (Acuity, Calendly, etc.) I don't see the picking up of the phone being removed from a franchised dealership anytime soon.
Do you guys remember GM's lovely 24 hour clock? And the ONLY iMR approved and Clock Stopping Tool you could use was ONLY available on a BlackBerry? No third party services allowed, no vacation responder tricks or you'd risk losing your EBE dollars.... This was 10 - 12 years ago. Now that was real full contact, hand to hand online selling! 2am a lead comes through, you respond, customer says "can you take a call," WHAT DO YOU DO? Money never sleeps.... You take the call.
Anyway, to properly handle a client, properly handle ongoing follow up and properly handle after sale follow up, deliveries, re-signs, issues and accessory jockying (all of which take a ton of time and falls on the salesman) I believe 60 leads is the number. Quality contact attempts, action plan actually being followed, true and meaningful connections, etc. Any less and they're not making money, any more and they're overwhelmed and quality of work suffers. Not to mention, internet or not, show me a single salesman not prospecting and selling 1 - 3 personally each month and I'll show you a salesman looking for a different job. So add those in there too.