I do commissions.
Why would you want one? Control.
What sort of control?
Quantity. If you look at my shop you will see a fair bit of yarn. You will also note that most are one-offs, of four to six ounces. Why? Because most folks sell color ways in 4-6 oz braids. I’m not going to plunk down 50-200 bucks to get a pound of it on spec.
Weight. I tend to spin more toward fine. If you want a yarn heavier than sport, you’re better off asking for it. I also, these days, am not aiming for gossamer*.
Twist. Most of my yarns are Z/S. If you knit continental, or crochet, or want to play with energised yarns, it’s a lot easier to order them.
Finish. Maybe you want to felt your project, or weave and full it. Those are better done with yarn plied a little differently, and not “set”. As a rule I set all my yarns, that ‘s a special feature (which doesn’t cost extra, but needs to be accounted for; as most folks expect set yarns, because commercial yarns are).
Special features. Do you want cables, thick-thin, high twist, pure worsted, long draw, etc? Those are easy to do, but aren’t my default.
Fiber. Merino is great, and BFL is lovely, but there are a lot of fibers out there. I’ve spun a bunch of them (from mink/camel/yak down, to mint/rose/milk cellulose; silk, alpaca, any number of rare breeds). If I can spin it, I will, but cashmere is pricey. When you factor the odds of my making the weight/twist/yardage you want, against the cost for me to whip some up on spec… best to just send me a query.
Color. Need 12 oz of saturated purple, and 6 of deep blue… I can do it, but it’s also not likely to be just lying around. It might build up (I’ve got 12 oz of violet getting spun up, but it’s not all the exact same fiber (I was playing with dying, and had three different protein/cellulose blend; two look very similar, the third is more different, even though the tone is much the same, the luster is not). I confess, I get bored. Without incentive** 1 lb of the same thing is going to get done in batches, with other things in between, which means I may sell off the first parts before the last are made and you can’t make those matching christmas stockings
That’s why you want to commission yarn
*not because I don’t like spinning it, but because it makes the yarn harder to sell, because it’s less versatile. It’s also harder to keep consistent, so I’m more likely to worry it’s not up to snuff.
**money is a great incentive