What is the salary and placement in iiser after bs-ms degree? Is its degree is helpful to study in foreign top university ?

Hello,

First of all; IISERs arent established to make people "just" earn after its BS-MS course (a common scenario in IITs and other engineering insti's ). The motto behind it is to provide high good quality education to young minds and drive the scientific attitude in them. As you observed, most of the grads apply for Phds (many are able to make through in international universities).
IISERs provide education in a fundamental way to its undergrads and there isn't much applicative approach adopted. Still I can just give a vague idea of jobs. The reason behind this rough idea is because at IISER, one is an independent fellow and not just tightened in his academic syllabus.You can opt for a wide number of courses. Page on iiserbhopal.ac.in
Thus you can be an expert in your field and this would then lead you to what jobs you may pursue.
On rough grounds; biologists , chemists can make it to some pharmaceutical firms. A friend of mine has been in a pharmaceutical and got a pay scale of 50k. mathematicians can work a lot in statistical works/firms , which ain’t bad at least in monetary terms. Physicists can work in lot of economic sectors .See Econophysics.
I know I haven't mentioned a particular range for the salary, because that's just impossible because of great variety(which I like the most of IISERs)