You're right in that it is pretty subjective. I would personally keep it simple in that $1 spent on content creation will generate X number of page views multip

You're right in that it is pretty subjective. I would personally keep it simple in that $1 spent on content creation will generate X number of page views multiplied by conversion rate to get you monthly revenue. Your new logic requires some sort of growth/decay rate which is mostly an assumption at this point unless you're willing to track that ongoing. However, to a startup and to high-level executives, it's not necessary. All they need to know roughly is how much investment is required to generate how much output and with the simplified model, it gets away from growth/decay rate discussions.