Does texting save money?

You apply for China Mobile M-Zone SMS package. 1. 10 yuan gives away 300 short messages every month (short messages can be exchanged with PHS customers of China Mobile, China Unicom and China Netcom, giving away the same number of short messages) 2. 20 yuan gives away 700 short messages (short messages can be exchanged with PHS customers of China Mobile, China Unicom and China Netcom, giving away the same number of short messages) 3. 30 yuan gives away 1000.