Sure you can ask the recruiter whatever you want. They only get paid if you take the job. You have a right to know how a transaction involving you is taking place - this is not the company buying deli meat.
Will the recruiter get upset? Maybe. If you are worried about this, then don't ask. But
But you have every right to ask and in my opinion every right to know.
If you find some intel on how the deal went down and they are outside of industry norms you may have more bargaining power. I for one have noticed that people who I interview through a recruiter are much more likely to negotiate their salary more.
The recruiter's equation is he gets a percentage of your salary or a flat rate. If you want too much company may lower percentage or may just not hire you. If you come in under he could make more. How much the recruiter works with you is directly related to their ability to find another person with little/no work.
Also if the recruiter knows how much you are going to make you are privy to the same info. Total nonsense if anyone telltells you different.