I can confirm that in this world that we live in, such practices are happening and bring good yearly revenues to many companies. There are companies (and I know from inside) that put their same product in different packaging and sell it for different price. It is the truth.
About Yamaha, I cannot tell. Maybe they do the same. Maybe not. Or maybe the truth is in the middle.
What I know is that indeed we live in the days when the memory cost is very low and should not be ignored.
For example, if we speak about the Wave ROM, the growth is normal to happen but do not expect miracles. R&D keeps the goodies until the competitors come to a certain level. The implementation of new technologies means also changes in production lines, which gives extra costs and mass production problems if it is not done correctly.
About the internal memory, because the thread is in the PSR S770-S970 zone: 13 MB it is very, very low. Nowadays 13 MB means nothing. Even if you utilize it for MIDI or Style files. For an arranger which has the .mp3 and .wav technology on them and no HDD or SSD capabilities, 13 MB is like a joke. For example Korg has in their PA600 2 GB of internal memory (and it is not a 2015 product). Internal memory for any arranger keyboard of any price level should not be less than 1 GB. This is a must. You don't have and cannot use a USB stick all the time: what if I have to use an iPAD and an external MIDI controller - what do I do then?
About the expansion memory, we have to give credit to Yamaha that coming from the last models there is a big improvement. Yamaha PSR-S950 and A3000 have 512 MB memory for new voices, which seems to be bigger than even the new flagship from Korg (PA4X, which has 400 MB).
Many users are more than satisfied with the memory they have. But the trend is for being able to customize you keyboard to your needs. And different people have different needs. Yamaha, most of all the others, understands that.
We will assist in the coming years to a lot and more technology improvements. For sure the competition is not sleeping. But Yamaha is on the right track. There is a lot of space to get better though.
If Yamaha will improve for the keyboards below the Tyros level and even for Tyros in: the memory size, style creator at a professional level, sampling import capabilities, touch screen technology with multitasking, real internal voice editing with real control (with possibility to save it, but not as a new voice), voice creator directly on the keyboards without need of a computer (with mono samples legato, with being able to establish sample loop directly from keyboard), Android and Mobile Windows support (for the devices that support core MIDI) - for sure will not have any competitor to be afraid of.
Also, if Yamaha started the Packs for different zones of the World, can improve and personalize even more (some really need improvement, mostly on the ethnic voices - some do not sound natural or are very different than the original instruments).