In [66]: a
Out[66]:
   Sales_1  Sales_2  Sales_3
0   200000   300000   100000
1   100000   500000   500000
2   400000  1000000   200000

In [67]: b
Out[67]:
            Commission
Sales
50000             0.05
250000            0.04
750000            0.03
9999999999        0.02

In [68]: c = b['Commission'][a <= b.index.values]
Traceback (most recent call last):

  File "<ipython-input-68-d229bce29f01>", line 1, in <module>
    c = b['Commission'][a <= b.index.values]

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreops.py", line 1184, in f
    res = self._combine_const(other, func, raise_on_error=False)

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreframe.py", line 3555, in _combine_const
    raise_on_error=raise_on_error)

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreinternals.py", line 2911, in eval
    return self.apply('eval', **kwargs)

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreinternals.py", line 2890, in apply
    applied = getattr(b, f)(**kwargs)

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreinternals.py", line 1132, in eval
    result = get_result(other)

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreinternals.py", line 1103, in get_result
    result = func(values, other)

ValueError: operands could not be broadcast together with shapes (3,3) (4,)

In [59]: a
Out[59]:
   Sales_1  Sales_2  Sales_3
0   200000   300000   100000
1   100000   500000   500000
2   400000  1000000   200000

In [60]: b
Out[60]:
            Commission
Sales
50000             0.05
250000            0.04
750000            0.03
9999999999        0.02

In [61]: c = b.lookup(a['Sales_1'],['Commission'])
Traceback (most recent call last):

  File "<ipython-input-61-99e8134e826c>", line 1, in <module>
    c = b.lookup(a['Sales_1'],['Commission'])

  File "C:WinPython64bitpython-3.5.2.amd64libsite-packagespandascoreframe.py", line 2649, in lookup
    raise ValueError('Row labels must have same size as column labels')

ValueError: Row labels must have same size as column labels

pd.cut(a.stack(), [0] + b.Sales.tolist(), labels=b.Commission).unstack()
Out[39]:
  Sales_1 Sales_2 Sales_3
0    0.04    0.03    0.04
1    0.04    0.03    0.03
2    0.03    0.02    0.04

Sales  Commission
0          -inf         NaN
1         50000        0.05
2        250000        0.04
3        750000        0.03
4           inf        0.02

pd.cut(a.stack(), b.Sales, labels=b.Commission[1:]).unstack()

pd.DataFrame(
    b.Commission.values[
        b.index.values.searchsorted(a.values.ravel())
    ].reshape(a.values.shape),
    a.index, a.columns)

   Sales_1  Sales_2  Sales_3
0     0.04     0.03     0.04
1     0.04     0.03     0.03
2     0.03     0.02     0.04

a_ = a.stack().sort_values().to_frame('Sales')
b_ = pd.DataFrame(dict(
        Sales=np.append(0, b.index[:-1]),
        Commissions=b.Commission.values
    ))

print(a_)
print()
print(b_)

             Sales
0 Sales_3   100000
1 Sales_1   100000
0 Sales_1   200000
2 Sales_3   200000
0 Sales_2   300000
2 Sales_1   400000
1 Sales_2   500000
  Sales_3   500000
2 Sales_2  1000000

   Commissions   Sales
0         0.05       0
1         0.04   50000
2         0.03  250000
3         0.02  750000

pd.merge_asof(a_, b_).set_index(a_.index).Commissions.unstack()

   Sales_1  Sales_2  Sales_3
0     0.04     0.03     0.04
1     0.04     0.03     0.03
2     0.03     0.02     0.04