Splitting, dividing & repotting
Most bulbs increase vegetatively; producing baby bulbs around the parent and gradually increasing into a clump. Snowdrops are no exception. In time, the clump can be lifted, teased apart and the separate bulbs used as the start of a new clump, sold or given to friends.
Unfortunately, the vast majority of snowdrops clump up at a rate that can be described as modest, at best. Herein lies the reason for their high cost. If you desire a specific snowdrop, then somone has to own a clump that they are willing to lift and plunder. The number of surplus bulbs that can be taken from the clump will be small and the remainder of the clump can then be replanted. The reduced, replanted parent clump will carry on but it will probably be several years before a further harvesting of surplus bulbs can be carried out.
The increase in number of bulbs is probably maximised if clumps are lifted every few years. In this way they don't have a chance to become congested and probably get ample air, water, light and elbow room. The downside is that this coincides with them beginning to form an attractive natural clump and look their best in a garden setting.
It is impractical to lift and separate snowdrops being grown on a landscape scale. You will have to rely on moles and other small animals to spread them around for you.
Reduced flowering
The flowering of snowdrops is controlled, amongst other things, by the diameter of the bulb. Unless bulbs are a sufficient width they won't flower.
When snowdrop clumps remain undisturbed over a long period, large congested clumps result. Many of the bulbs will be long and thin, squeezed by the numerous other bulbs in the clump. These narrow bulbs may be equivelant in weight to a normal bulb but are not wide enough to flower. Hence, large old clumps of snowdrops will have a preponderance of leaves and relatively few flowers.
Pot grown snowdrops
Pot grown snowdrops should be repotted every year, when dormant, into fresh compost.