Why are you complicating things, industry standard when selling bandwidth is in bits.
A megabit is styled as “Mbps.” A megabyte is abbreviated as “MBps.” That small capitalized “b” makes a world of difference.
So your packages are...
256KBps equals 2048bits or 2Mbps. = 2,000/-
512KBps equals 4096bits or 4Mbps. = 3,000/-
1 (1024)MBps equals 8192bits or 8Mbps = 5,000-
Simplify and get sales.