Attributes With Costs

Decision Tree Learning

For example, in the medical field applying a test costs money, in a robotic setting applying a test takes time and power.
How do we learn a tree that also minimizes cost?
Replace gain by \[ \frac{Gain^{2}(S,A)}{Cost(A)}. \] or by \[ \frac{2^{Gain(S,A)} - 1}{(Cost(A) + 1)^{w}} \] where $w \in [0,1]$ determines importance of cost