1.. Hmm, how to say this delicately ? The girl has breasts that are appreciated by the guy, even if they are not as large as he would like. This would probably not be said in mixed company, but between (some young?) guys.
2. plus one. When you get an invitation to a wedding, usually you are invited and your partner (wife or girlfriend) is included. The wedding invitation may say "Andrew plus one" meaning plus one extra guest, being my choice of who to bring with me.
3. $200 a plate, means that catering for each guest costs $200. So in this case, because it is so expensive for catering, the "plus one" guest is not included in the invitation.
clear ?