Not three models, nine models (3 species x 3 ages) Well normally (without the sale) the ratio is 5 single species (15 models) = a library. Of course it is always a better bargain to buy a library than single models. But cases may happen when someone does not care about one library, except for a couple of species. Say you don't like or need tropicals except for the Coconut palm and Sugar Cane. In that case, you have the option of buying only the two species that you wish/need and save (in case of two species) 71 dollars, which is not bad - it's half the investment you can make in a different full library.