well 25$ for writing 5 lines of command into a file is quite astonishing rip off. Its like the guy who sold 1 pixel worth of advertisement on his site for a dollar,
or the guy who said donate 10000$ or ill kill this bunny...
example applescript:
CODE
on open filelist
repeat with i in filelist
do shell script "render -r mr " & POSIX path of i
end repeat
end open
That is assuming you have configured your shell to include the maya path if not then just type the full path of the maya install bin dir in between " and render.
PS. i made the astonishing assumption you want to use mental ray