I also think an important motivation for building RTOs is real estate proftlits. And orphancrow has a good hunch about getting Satan's governments to support their work. In addition to getting government aid, it can also help Watchtower avoid getting taxed, since they can point to these efforts to support smaller languages, some of which are dieing. Look, we really are a charity!
Geoffrey Jackson has some direct experience with tapping this revenue stream. He was able to get the Australian government to foot the bill for publishing his Tuvalu an dictionary, when he was a missionary there. Tuvalu has the smallest population of the 196 members of the UN. And only 10,000 people speak Tuvaluan. But look at all the literature published in Tuvaluan on their website. All that for one congregation with 60 publishers.