No discernible benefit??? It liberates three times the number of channels in an already congested spectrum - something that's both a benefit and discernible, surely?
The different prices for equipment mods will reflect the different components that need changing - with some it's just uploadable software, with others it may need an eprom change, with yet others it may need some glue logic chips changing and with some it may even need changes to the RF boards to cope with the tighter bandwidth limits. And then there's the detail that some may need changed displays and switchgear.
And then there's the detail that the cost per unit will also depend on how many of the upgrades they will sell and so how much the basic engineering/qualification/tooling costs can be divided amongst those individual sales. With the newer units this could simply be the number of units installed as people will tend to bite the bullet and spend the money on new kit. But if it's older kit then it's quite likely that people will choose to replace it with something new and blingy rather than upgrade it, so the number of upgrade sales will be less predictable.
The fact that the upgrade costs are actually different tends to suggest they are representative of the actual costs rather than being random numbers...
PDR