Quine multiple times
CJam, 28 26 bytes * 0.9 = 23.4

Thanks to Sp3000 for saving 2 bytes.

{`"_~"+rd_z26*,\g1|@%f=}_~


Test it here.

Explanation

{`"_~"+ e# Generalised quine framework. Leaves the source code on the stack.
  rd    e# Read input and parse as double.
  _z    e# Copy and get absolute value.
  26*   e# Multiply by 26, the length of the quine to get length N of the output.
  ,     e# Get a range [0 1 ... floor(N-1)].
  \g    e# Swap with other copy and computer signum to determine direction of string.
  1|    e# This might be zero though, so take bitwise OR with 1 to avoid an error.
  @%    e# Pull up source string. Reverse it if the signum was -1 (no-op otherwise).
  f=    e# The range we pushed earlier corresponds to the (cyclic) indices of the source
        e# which make up the desired result, so we map each index to the corresponding
        e# character to get the final result.
}_~