Most domain names are around $10-15, not $20 as the host said. The top two registrars are GoDaddy and Enom/TuCows.
With us (ENOM), .com and.net are $12. GoDaddy does a bait-and-switch, offering domains for $1.99 which renew at $16.
Web hosts can provide email services as well as the domain registrar and outside resources (Microsoft Exchange, etc.), but many do not allow mass marketing (sending) which is why ConstantContact is necessary.
For some (Iike us) basic email is FREE with hosting (30 mB), 10-20 accounts depending on the hosting level (starting at $10/month). ENOM charges $1 per month per address (12 GB). GoDaddy charges around $2 per month.
It is also possible to read/store/reply to hosted email FROM INSIDE GMAIL.
Not all email providers include Alias options, but when available, lots of ALIAS email addresses can be added to any root @email. It's very useful for source tracking and spam management. An alias can be instantly removed along with all the spam that comes to it.
An added security feature is that an alias email address cannot be used to log in or send: right key, wrong door. My email alias is email@example.com. If you knew my email password you could not log in or access my email.