The big insurance companies (all those HMOs and PPOs) have profoundly affected how therapists are paid. In reality, it's not unusual for therapists to make between $35,000 and $55,000 a year. (More than your average startup writer, granted!)
To put that in perspective, though, if you can write JavaScript, C++, or PHP, you can easily make more, and you don’t even have to have a college degree (though certainly one tends to be preferred). I know exceptional therapists who carry a full case load and still make only $25,000 to $30,000 a year.
While $100 an hour may seem steep, the only money therapists make is during client sessions. Therapists don’t get benefits, health care, or retirement plans from their employers (if they even have employers). In fact, if a therapist works for a practice owned by someone else, the employer may take 50% or more of what the therapist makes for each client seen.
Add that to the fact that insurance pays therapists a reduced fee for each session (say $40 to $80, though it can be less)—and suddenly that $125/hr you think your therapist is pocketing becomes $20 or $30 at most—a rate that’s comparable to skilled construction workers (e.g. brick masons, boilermakers, elevator installers).
Now, the longer one practices therapy, the more likely one is to start a practice or move into a position as one of the primaries, so as a client base grows, one's salary will also go up—but again, that can take years and often decades.
The Occupational Outlook Handbook 
provides good general information on job earnings and requirements. (If you've never visited, it's a great resource.) Here are some entries; everything in italics is a direct quote.
Median annual earnings of wage and salary clinical, counseling, and school psychologists in May 2004 were $54,950. The middle 50 percent earned between $41,850 and $71,880. The lowest 10 percent earned less than $32,280, and the highest 10 percent earned more than $92,250. Median annual earnings in the industries employing the largest numbers of clinical, counseling, and school psychologists in May 2004 were:
Offices of other health practitioners |
$64,460 |
Elementary and secondary schools |
58,360 |
Outpatient care centers |
46,850 |
Individual and family services |
42,640 |
Annual earnings of computer software engineers, applications ranged from less than $50,270 for the lowest 10 percent to more than $116,340 for the highest 10 percent in May 2004. Managers usually earn more because they have been on the job longer and are more experienced than their staffs, but their salaries, too, can vary by level and experience. Accordingly, annual earnings of computer and information systems managers ranged from less than $65,800 for the lowest 10 percent to more than $145,600 for the highest 10 percent in May 2004. Earnings also may be affected by size, location, and type of establishment, hours and responsibilities of the employee, and level of sales.
In May 2004, full-time wage and salary paralegals and legal assistants had median annual earnings, including bonuses, of $39,130. The middle 50 percent earned between $31,040 and $49,950. The top 10 percent earned more than $61,390, while the bottom 10 percent earned less than $25,360. Median annual earnings in the industries employing the largest numbers of paralegals in May 2004 were as follows:
Federal Government |
$59,370 |
Local government |
38,260 |
Legal services |
37,870 |
State government |
34,910 |
A high school degree is not required.
Median annual earnings of Postal Service mail carriers were $44,450 in May 2004. The middle 50 percent earned between $37,590 and $50,580. The lowest 10 percent had earnings of less than $31,980, while the top 10 percent earned more than $54,240. Rural mail carriers are reimbursed for mileage put on their own vehicles while delivering mail.
