Regardless of which animal products you buy, one thing should always be the main deciding factor: animal welfare.
In order to be able to produce as cheaply as possible, some producers resort to farming methods that are not necessarily animal-friendly, to put it mildly.
With alpacas, it is particularly important that they are herd animals and need a lot of space to graze. While being locked up alone, wooden sheds may be convenient for the producer, but it is certainly not good for the animals.
Impossible trade-offs are often made in feed and hygiene as well, such as cheap feed instead of grass and quick improper shearing methods instead of regular, well-groomed shearing.
So when buying, try to find out if the manufacturer of the blanket pays attention to such things when buying his wool from the producers.
Then you can really snuggle up in your new blanket with peace of mind, without having a guilty conscience that possibly an animal had to suffer for your comfort.