Plesk is a paid control panel, but, they have a free one-email & one-domain version that is default when you install it without a license key. After that, you just add a license key and upgrade your limits (starts at ~$200).

Plesk, cPanel and DirectAdmin are the three worth looking at imo. The pricing for control panels will usually always be cheaper from the server supplier ('internal rates') rather than the 'external retail rates' - e.g. cPanel is $20-30 per month from dedicated server suppliers when purchased with a server, but, if you are buying a license elsewhere, expect to pay around $50/mo