This is a topic I've thought deeply about for the last 15 yrs. It's such a complex topic, because there are so many unknowns and moving parts.
Let's dive in:
The prob is that when you first start, you don't actually know how much they are worth to you. On the cost side, that will vary widely based on channel
First, there are a LOT of great blogs that you should read on cust acq - esp SaaS cust acq:
-SaaStr.com
-Forentrepreneurs.com
-christophjanz.blogspot.com
& more
So what do you do if you are in this boat?
For ex, if I am selling a widget for $50 (after COGs), then conservatively, I should assume a customer will buy 1. And I should spend < $50 to get him/her.
But if you are building a capital efficient co, this is the characteristic most of them have. And in this mkt, where it's hard to raise, this is impt
Why? If you want to scale up your paid, you need to know the true cost of paid.
If you have that, then that is magical, and you should definitely keep pouring $ into paid until those conditions change.
This is where rev based financing can help in mkts like now where VCs are more conservative. You can get a line of credit now just based on your #s & keep going.
The unspoken thing about mktg is that mktg channel arbitrage opportunities are a bit cyclical.
Mktg channels are like stock market arb opps. Demand for different channels affects pricing, and demand is always changing.
In these mkts, I've heard from a # of portfolio cos that their CAC has gone down in paid channels. My guess is that lots of companies are pulling back on spend.
But MOST channels are paid. If you hire writers to help w/ SEO, that should be considered PAID - there is a cost.
If it's you doing the work as an unpaid founder, you need to use market rates (i.e. what you'd pay someone else) to compute this paid acq #. It's NOT FREE.
Ideal mktg:
a) Segment your mktg channels
b) Compute TRUE acq cost by segment
c) Scale up 1-2 channels that yield immediate payback on first sale
d) As you get more data on retention, extending payback period is ok
e) Channels will get saturated but revisit later.