The recommendation below is an advertisement. Most of the links here are part of Amazon's affiliate program (unless otherwise stated), which helps support this website. It's also more than that - it's a hand-picked recommendation of something I've used myself. If you're interested, here is a full list
Drawabox-Tested Fineliners (Pack of 10, $17.50 USD)
Let's be real here for a second: fineliners can get pricey. It varies from brand to brand, store to store, and country to country, but good fineliners like the Staedtler Pigment Liner (my personal brand favourite) can cost an arm and a leg. I remember finding them being sold individually at a Michael's for $4-$5 each. That's highway robbery right there.
Now, we're not a big company ourselves or anything, but we have been in a position to periodically import large batches of pens that we've sourced ourselves - using the wholesale route to keep costs down, and then to split the savings between getting pens to you for cheaper, and setting some aside to one day produce our own.
These pens are each hand-tested (on a little card we include in the package) to avoid sending out any duds (another problem with pens sold in stores). We also checked out a handful of different options before settling on this supplier - mainly looking for pens that were as close to the Staedtler Pigment Liner. If I'm being honest, I think these might even perform a little better, at least for our use case in this course.
We've also tested their longevity. We've found that if we're reasonably gentle with them, we can get through all of Lesson 1, and halfway through the box challenge. We actually had ScyllaStew test them while recording realtime videos of her working through the lesson work, which you can check out here, along with a variety of reviews of other brands.
Now, I will say this - we're only really in a position to make this an attractive offer for those in the continental United States (where we can offer shipping for free). We do ship internationally, but between the shipping prices and shipping times, it's probably not the best offer you can find - though this may depend. We also straight up can't ship to the UK, thanks to some fairly new restrictions they've put into place relating to their Brexit transition. I know that's a bummer - I'm Canadian myself - but hopefully one day we can expand things more meaningfully to the rest of the world.