Kilo is always 1000 
1kB is therefore always 1000 bytes (powers of 10). However, 1KiB (kibibyte) is 1024 (powers of 2). The metric system is kind of a mystery for the Americans, and indeed, some products mix these up and use 1024 as a “kilo” byte.
It also depends on what you measure. Bandwidth is always in bits (because you transmit one bit at a time). Memory (cache/RAM) is usually in powers of 2. And storage usually in powers of 10.