Pantone and Nekopiko are cheap alternatives. However, they're definitely subpar in quality compared to copic. You get what you pay for I guess. Prisma is nice, but it's also expensive. Plus they're smelly. I used to use them but i just couldn't take the smell...
If you're new to manga and comics, I'd recommend using watercolor. If you use a higher concentration of watercolor when you paint, you can achieve a marker-like effect. Or splurge an extra few and buy some gouache watercolor, which is more opaque than regular watercolor. Watercolor is definitely cheaper and easier to use. You can buy a cheap pack of only several colors and just mix them until you get the right colors you want. Most professionals who color traditionally use watercolor. For instance, Takano Ichigo. This is kinda a generalization but from what I've seen, most shounen jump authors use markers to color. Probably because it's faster since you don't have to wait as long for it to dry. They do have more insane deadlines than most others.
Markers can bleed easily and dry out. Plus it's hard to blend colors and you have to buy bristol smooth paper, which can get costly. I really don't recommend it unless you like the marker effect a lot. But then again, if you're willing to spend so much on markers just spend the money on buying a tablet and a drawing program. Most drawing programs like SAI or ClipStudio have brushes with marker effects.