Hello,
currently, Poppy creatures are using motors from the Robotis Korean company.
For the high-end creatures like Poppy, we use:
They are very good, but nevertheless quite expensive. For schools, projects using only one arm of the Poppy humanoid could be done, costing about 1000 thousand euros for motors and 3D printing.
Some people in the community are researching how to use alternative cheaper solutions, e.g. see the topic:
We are also going soon to develop new low-cost creatures based on Robotis XL-320 motors:
http://support.robotis.com/en/product/dynamixel/xl-series/xl-320.htm