There are many options for small factory units all over the world now. These can vary in size and skill with maybe 10 or less staff.
They will generally have access to most of the industrial machines you will need for your products and have contacts for additional services such as printing and embroidery companies that will also do smaller scale orders.
If you use a small factory, they will be able to produce on mass but at the lower quantity range, so anywhere from 50 to around 200 pieces, although the upper limit will depend on the factory itself. The length of time this will take is obviously quicker than individuals who wouldn’t be able to do such a large order, but won’t be as fast as a large factory. So you will need to factor in extra time for production.
Price is usually cheaper than a dressmaker because you are buying fabric, components and making on a larger scale, however, it’s important to know that the larger the order, the less money each individual product will be.