Cordura, which is what most robust backpacks are made of, is surprisingly expensive.

Yeah, I checked prices for ripstop nylon when I posted. Cordura doesn't seem to be a whole lot more expensive than I said.

http://www.rockywoods.com/Fabrics-Kits/1000D-Cordura-Nylon

It's also heavy. A better choice for this person's application would be Tyvek. (e.g., https://backpackinglight.com/forums/topic/18758/ ).

Maybe the licenses for the patterns I was buying it with pushed my prices up.

It's also incredibly heavy. There's a reason why no ultralight backpacks use the 600-1000D Cordura that more robust bags are made of.

You can find it very cheaply in some cases. I once called a ripstop manufacturer and got 75 yards of slightly miscolored fabric for free.

Tyvek would probably make more sense for a project like this. $30 will get you 10 yards on Amazon

Tyvek is loud. I used it to sew furniture covers for a cabin that is left unoccupied in winter. Shaking out the bed covers to put them on is deafening. Walking with a Tyvek pack might drive you mad.

Those IKEA bags are pretty freakin loud too. Both are materials I wouldn't want near me.

I don't think tyvek would be strong enough for a backpack. It is used a lot in backpacking for ground sheets and even shelters.

Tyvek also breaks down in UV light.

He paid $6 for the bags, so it may have been cheaper this way and/or more convenient.

Oh, it was obviously cheaper. But he spent 25 hours stitching. If I were doing that, I'd spend $25 getting the properties I wanted.

I think it looks pretty cool. And now he has the knowledge of how to make the backpacks without mistakes, so he can move onto more expensive material with confidence.

If your hourly rate is $10 dollars an hour, then that works out as a fairly expensive bag!

If you do it in your free time, it's an extremely cheap bag. People tend to overestimate the value of the time they spend not earning.

If you're spending that free time with family or friends or doing something else you value significantly, then sure, there's value to that time. If you're browsing photos on Reddit or watching TV, it's probably not that valuable if you honestly evaluate it.

Plus, you can get exactly what you want. There's such a rush from creating what you really want, and you get a little bit of that rush every time you look at your work again.

It is easy to consume. To create or make is so much harder, getting exponentially harder the higher the final quality needs to be.

Anyone who has ever burnt or messed up their dinner while cooking and still ate it will attest to the power of personal time investment.