Which insurance plan do you have? For mine (company-controlled PT), in-network providers cost $10 per visit + 10% of testing & diagnostics, although the testing & diagnostics are often covered in full. In other words, the cost should be minimal.
Just any FYI: Most people do sore in their sleep, and sleep apnea has been identified as being over diagnosed (big $$$ in equipment, although your insurance will pay for most, if not all, of it). Proceed with caution -- if your son is young, it may be best to let him decide what's right for him when he gets older.