I think Tonga Batiks is just the name of that company. It is not an indication of where the batiks were manufactured. Although batiks originated in Indonesia (I used to live there), most fabrics sold as batiks today are probably manufactured elsewhere. Quality is not necessarily dependent on where the batiks are made, but rather on the processes and quality control used in the making. Even with batiks made in Indonesia, there can be differences in quality. How you measure quality is an issue also. Hand-painted batiks are definitely more expensive; are they higher quality? Batiks made by hand with a copper tjap - would you consider this to be a higher quality than a batik made in a factory with an imprinting tjap?
Most of the differences between batiks sold in the U.S. are in the designs and colors -- not in the quality of the griege goods or the dye process. You have to decide if you like how the individual fabrics work together. It is definitely not necessary to buy a "coordinating" set of batiks from a single manufacturer, for example, in order to create a gorgeous quilt.
Batiks are usually printed on a higher thread-count fabric than other cottons. However, lots of people mix batiks with non-batik cottons in quilts.