Business Connectivity → Traditional Dialer or Mobile Dialer

I used "My Sales Dialer"; an android based app available for only $9.99 one time fee. It turns your android phone into powerful dialer.
I am making 200 calls per day and before was only able to do 40-50. I have unlimited data+text plan from T-mobile for $49.99, so there is nothing extra I am paying to get my work done.
Now I am planning to buy 50 more "My Sales dialer" for my team.

Why we should pay more to PC based dialer when we are getting more facilities in $9.99??

K.A.