[munger]

I tried my hand at a couple affiliate marketing style blogs thinking the same thing - I'm a web dev. Never made more than a couple hundred dollars over the course of months of occasional fiddling.

You have to love writing, what you are writing about, self/product promotion and project management like outsourcing tedious SEO things for cheap otherwise it will rarely amount to much.

If you are a developer and love these things, then sure it would be great if you could spend an extra hour or two for some months to make $36k in addition to a regular income, but I would say the kind of effort and results achieved by OP is an outlier. YMMV even if you have all the skills.