|My experience with cell phone batteries is that once a particular model has run its course, the batteries become surplus and therefore cheap. I once bought OEM batteries for my Motorola Razr phone for $6 for a 2 pack. Still using them too.|
When you buy a new model the only batteries that most likely will be available will be from the original equipment manufacturer, which will make them more expensive.
My advice is to use the battery life in hours of use to select the model. By the time you need a replacement battery they will be cheaper. The more popular the model was/is the more available replacement batteries will be. Some major manufacturers use the same battery for many different models.