Often some of the best play is the least expensive!
These are great for early language users because they really lend themselves to some fun "doing words" (like "shake", "roll", "bang") and noise words (like "splash" and "ding"). For children with more language, getting them involved in making these toys give them the chance to practice following instructions and using sorting skills and language (think shapes, colours, size). For the babies, they might just buy you a few more minutes of tummy time!
If you make pairs of each, this could be an opportunity to practice some non-verbal imitation (great for developing early social skills). I'd love to see yours in action - tag me in @learngrowspeech or #speechiemum