Well, for starters, most radiology residents do not earn that much during residency. For example, at Virginia Commonwealth University, the radiology residents are paid as follows:
PGY 2 – $46,026
PGY 3 – $47,684
PGY 4 – $48,581
PGY 5 – $50,808
By most Americans' standards, these salaries are reasonably competitive. However, given the additional hours of work and call that residents suffer through, the salaries approach minimum wage when considered on an hourly basis. Imagine if a residency works on average 60 hours a week for 48 weeks a year. The total hours, 48 x 60 = 2880 hours. At a salary of $48,000, this works out to $16.67 per hour before taxes. While these numbers are used solely for demonstration, many residents would agree that the pay is not as competitive, especially when compared to other professionals with graduate degrees (JD, PhD).
At many institutions though, the salary can be augmented during residency. The first method is to provide the residents with a book fund, anywhere from $500 to $2000, that can be used to purchase textbooks and other educational materials (including laptops in some cases). The second, and potentially most lucrative method, is through a process known as moonlighting. Often performed by third and fourth year residents, moonlighting can either be performed within the hospitals affiliated with the program or externally at another, unaffiliated hospital. During the moonlighting, the resident can perform a variety of tasks, just as a fulltime radiologist would, providing that they have the appropriate insurance coverage and license. Moonlighting can pay quite well, with some places offering up to $1000 per night of work. The resident still has to abide by resident work-hour restrictions, as well as by any restrictions imposed by the residency program.
When you consider moonlighting opportunities, a resident who decided to utilize them religiously could conceivably make over $100,000 a year. However, the reality seems to be that this is true of only a few residents, mostly those with families or large debt who really need the funds. The majority of residents who are able to moonlight seem to do a small amount, simply to supplement their income or have a little extra spending money. Ultimately, the compensation one receives when one starts to work full-time as a radiologist will dwarf the amounts involved during residency, but it is reassuring to know that there are avenues available to supplement your income as a radiology resident.