Why there is no universal number
A $500 CAC is fatal for a $9/month tool and absurdly good for a $50,000/year contract. CAC only means something next to what the customer pays you, which is why the useful benchmark is CAC payback: CAC divided by monthly gross profit per customer. Under 12 months payback is good for SMB SaaS, under 18 is acceptable, and enterprise deals with multi-year contracts can tolerate 24 or more. Payback tells you how long your cash is locked up, which is what actually constrains growth.
Typical CAC bands by ACV tier
For self-serve products under $1,000 ACV, CAC typically lands between $100 and $600. SMB SaaS at $1,000-10,000 ACV usually sees $500 to $3,000. Mid-market at $10,000-50,000 ACV runs $5,000 to $15,000, and enterprise deals above $50,000 ACV commonly cost $20,000 to $100,000 or more to close once sales salaries are counted. These are rough bands, not targets; a CAC far below the band for your tier usually means an unscalable channel, not unusually good marketing.
When this number lies
Blended CAC mixes free organic signups with paid ones and can make a broken paid channel look survivable. Excluding salaries and founder time is the most common distortion; a founder doing all the selling has a CAC near zero on paper and a very real one in practice. Early customers from your network, community, or a launch spike are cheap and unrepeatable, so CAC from the first 50 customers rarely predicts customer 500. Measure paid CAC and blended CAC separately, fully loaded, and trust the trend more than any single month.
What to do with this as an early-stage founder
Before you have stable channels, obsessing over CAC is premature; the honest early question is whether anyone will pay at all. Once a channel produces customers repeatedly, compute payback on that channel in isolation, and kill or fix anything beyond 18 months unless your ACV justifies the patience. Keep gross margin in the payback math, because a customer paying $100/month at 70% margin returns $70, not $100. Cheap CAC on a product nobody retains is still a dead business.