The above indicates that there is/are a lot of N: N is repeated many times; there is (almost) nothing but N. The use of ばかり conveys the speaker's feeling that it is not very desirable for someone/something to be limited to N.
家の回りは田ばかりです。
There are only rice fields around the house.
毎日雨ばかり降っています。
It keeps raining every day.
先生はわたしにばかり質問します。
My teacher asks questions to nobody but me.
Lesson 6-10「学生は日本人だけですか。」
Are all the students Japanese?
Lesson 15-6「わたしは安い物しか買いません。」
I only buy inexpensive things.