Domain transfers cost money at every hosting company because they extend the expiration date of your domain for 1 year as it is technically renewing it when it transfers.
There might be some exceptions to these rules as some gTLDs (Geographic Domains) won't extend the expiration date during the transfer. The following gTLDs won't be extended when they are transferred:
Americas: .cl, .com.ar, .com.br
Asia/Oceania: .co.nz, .com.au, .com.sg, .jp, .net.au, .net.nz, .org.nz, .sg
Europe: .ch, .co.uk, .es, .fi, .me.uk, .org.uk, .se, .nu
You do not need to transfer your domain to us in order to use our service, you can simply change the name servers to ours which will work the same.