Based on a few anecdotal cases, here are some possible reasons why someone (say Candidate ABC) without much Wall St track record can get $100/hr.

Reason: hiring mgr has unusually high budget. Such jobs tend to be kept in secret. Few candidates get to know about these openings.
Reason: hiring mgr releases the opening to a single favorite recruiter. This breaks the rule that “the higher you pay, the more quality candidates you attract”
Reason: hiring mgr is lazy or in a hurry or both
Reason: hiring mgr is inexperienced and doesn't know how to find a good number of talented candidates. He ends up interviewing many sub-standard candidates and is impressed with a candidate like you and me
Reason: hiring company has a history of paying $100+, so $100 is easier to approve. More likely a small company. I avoid small companies.
Reason: most candidates don't insist on $100/hr. They try for a while then lower it to $80 so they are never shortlisted for $100 jobs.
Reason: (my guess) hiring mgr wants to test drive the candidate for a short few months and “recycle” if necessary, so value-for-money is less important.
Reason: ABC knows a large number of recruiters with lucrative positions. This requires effort.
Reason: ABC prepares very well for standard java questions. No work experience in finance required.
Reason: (my guess) ABC is seen as someone special and leaves a lasting impression on hiring mgr
Reason: ABC has a very high previous salary so his asking price is justified.
Reason: hiring mgr just lost a key developer and is looking to hire a competent replacement
Reason: hiring manager doesn't care about value for money — not his money