if you want to compute for 0 dollars per month, buy a decent laptop and go to star bucks and libraries.
In addition, Starbucks -- at least the one near me -- doesn't allow you to occupy a seat without purchasing something and since the Internet service offered there is subsidized by coffee ... very expensive coffee, at that ... the cost of using Starbucks[0] daily for 5 business days/over 4.5 weeks/month assuming you get away with buying only one Venti Starbucks regular coffee at USD$2.45 is about the cost of broadband at home, not including fuel to drive there and back (assuming you didn't walk/ride a bike)... and there's no preemptible VMs included with the brew.
[0] I skipped library internet access because, at least for me, the performance is so bad at my public library I wouldn't consider that viable Internet service. And it smells like books there.
Probably because you didn't include the laptop's price. If you spent $300 and it lasts you four years, that's already $6.25/month. Sure you get internet access for free, but so could the author, it's not like you can't take a Chromebook to Starbucks or the library.