The wild west is the standard way that agencies get contracts with hospitals and traditionally these contracts are all written by the individual agencies. As such, bill rates can vary wildly depending on multiple factors including negotiation abilities and quality of travelers presented and supplied. For the most part, managers could care less about a few dollars an hour for the right candidate, but HR and the bean counters do care quite a lot. To the extent that they can, they may exclude profiles from high bill rate agencies from reaching the manager. In addition, working relations can be different between the hospital and different agencies. Thus, the choice of agency you pick to send your profile to the hospital may affect your ability to get an interview.
Bill rates are sometimes provided per candidate, or must be renegotiated on some schedule. Depending on where an agency is in that cycle may dramatically vary the competitiveness of the rates they offer travelers. And again, how good an agency is with negotiation and keeping up with these issues, not to mention the quality of the travelers they have historically provided, makes a lot of difference.
High needs hospitals will often provide their own contract with uniform bill rates, or utilize a prime vendor with uniform bill rates. It is great to know when this happens because now you can really compare the pass through rates of different agencies. If you have primarily worked only hospitals with a lot of travelers, it is less likely that you would see this kind of spread between agency offeres.
Agency compensation will still vary on a number of factors of course, the gross profit margin they require, and the value of various benefits. Gross profit margins vary from 15 to well over 30 percent of the bill rate (the rest of the rate is passthrough compensation to the traveler) - average gross profit percentage was 22 percent prior to 2008. If you look at a typical bill rate of $60 an hour, that gross profit margin runs from perhaps $10 to $20 an hour. So there can be a lot of room there too in affecting the pay of travelers at the same facility with even the same bill rate.
The benefit and compensation analysis is where many travelers and recruiters can have a communication failure. It is rare to have an $8 real difference in total agency payout because of competition but it does happen. PanTravelers has an excellent calculator that will put different offers on a level playing field to determine which complex offer is really the best. It is possible that the low pay recruiter missed mandatory insurance, or per diem reimbursements. Or they had an unrealistically low housing stipend but actually would provide great housing. Lots of possibles.
There is often a communication problem between hospitals and agencies. So much so that some agencies will not even rely on hospital information to post a job, but base it on another agency's ad for a hospital that they have a contract with. So they can miss when a hospital increases their bill rate for a rapid response job and insist on the lower rate without real knowledge. (This same issue can cause a recirculating fake job that is only found not to exist after a profile is submitted).