That said, if you already have working redirection service, there is no need to change it.
Unless they charge you $10 for the domain renewal, you local provider is trying to rip you off.
Change them.
All that you have to do for redirecting is to have the extra domains pointing to the same DNS servers as the original domain.
One advantage of using the redirecting system is that you can have email addresses for both domains upto the limit of the main domain. So if you have 5 email addresses permitted you could have 3 for the main domain and 2 for the domain added on.