The first point is that the manufacturing process is very different. Some are made by hand, so the cost will be higher, and some are made by machine, so the cost will be lower, so the price will be different.
And the origin of sweet potato vermicelli. Because there are many producing areas of sweet potato vermicelli, the quality of vermicelli there is relatively better, and the price is higher than other places, because the soil and water there are very suitable for planting sweet potatoes.