If the employees learn something which they can then bring back to the company and use when troubleshooting or performance tuning then yes it is worth it. If the employee happens to get certified in the process then that’s even better.
I’ve seen the money handled a couple of ways in the past.
1. The company just pays for everything.
2. The employee fronts the cost, and upon successful completion and a passing grade the company reimburses the employee for the costs.
3. The company splits the cost with the employee.
4. The company tells the employee to pay for it them selves.
With options 1 and 2 your employees will be most happy. Some companies require that the employee sign a contact not to quit (may or not actually be enforceable in your state or country) for N number of numbers after the training to ensure that the company gets their money worth. This can make the employee week like crap, so use with caution if you decide to do this. Obviously you can only ask the employee to sign something like this if the company covers all the costs up front.