No doubt espresso/coffee gets expensive, but I would argue that it pays for itself.
Being self-employed at this juncture, I have found that to be productive requires a plan. Secondly, I need small goals (weeks) rather than long goals (months etc...). Four hours ago, I had no plan for the upcoming week or any energy/motivation to be productive.
Enter one $4 double tall soy latte. Now, at 1am I now have a good start on the week ahead with energy to spare for a quick blog.
It may be unfortunate that caffeine is my effective catalyst for efficiency, but the fact remains.
Conclusion: $4 well spent.