Researchers don't get money from the journals, we usually pay to publish there. Actually that depends on the country, but even in the USA where a lot of research is funded (but not necessarily conducted) by private agencies governmental fundings make out a significant amount. That being said, many governmental funding bodies like e.g. the NIH require that the publications of research funded by them has to be openly accessible. Whether the costs that journals charge is justifiable is debatable. However open journals are in the rising. Some, like e.g. PloS or certain BMC journals even have a very high impact factor.