Title text:
Detectives say the key to tracking down the source of the kites was a large wall map covered in thumbtacks and string. 'It's the first time that method has ever actually worked,' said a spokesperson.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3121/
Doing some quick math here:
Circumference of the Earth is about 24k mi = 44M yds.
The cheapest fishing line I could find online (from Amazon) (I didn't search very hard though) was $10 for 440 yds of line. To circle the Earth, you'd need 44M / 440 = 100k spools = $1M for the fishing line.
Let's assume every spool needs about 1 kite. That's 100k kites. You can find kites online for like $5 each, but the cheapest way to get a kite is probably to bulk order wooden sticks and plastic film and make them yourself. Let's do the math on that.
Assume each kite requires a generous 5 ft^2 of film, and 10 ft of sticks. I found some bulk plastic film rolls online (from McMaster Carr) for about $0.02 per ft^2, and some wooden marshmellow sticks (on Amazon) for about $0.10 per foot. That makes $0.02*5 + $0.10*10 = $1.10 per kite. That totals $1.10 * 100k = $110k.
So using these estimates, this kite ring costs around $1.11M.
No clue if it would actually work though.
Edit: corrected a math error
This also assumes the time you spend making 100k kites is worth nothing to you. Say you can make 20 kites in an hour (1 every 3 minutes), and you work for 15 hours every day. It will take you 333 days to finish that on your own.
We just need a few hundred people working on them. 300 kites per person is much more doable. Even better, I'm sure we could find some place overseas where we could hire help to assemble them for relatively low cost
that's just the $5 kites with more steps