In small towns it is difficult to find affordable gardening supplies locally and ordering live plants online can be very expensive due to a number of factors like
Transportation cost
Damage to the plant
Packaging required
Unlike non living items like electronic items, clothes, accessories, the plant will have to be watered daily if it is being transported a long distance. So the plant seller will have to take this fact into account while pricing the plant being sold online, as they cannot be sure of how many customers they will be getting