With Milly Alcock's Supergirl making a surprise cameo appearance at the end of James Gunn's Superman -- one of this year's biggest blockbusters -- and the DCU's Supergirl: Woman of Tomorrow currently in production, Supergirl is hot right now. If you take a close look at GoCollect's Silver Age Collectible Price Index (CPI), you could make the argument that she's been hot for years.
Let's a take a deeper dive into the CPI. Since achieving a record-high in June 2022 during the pandemic-fueled "comic boom," most major Silver Age keys have been mired in a long-running bear market for the past three years with the index shedding about 21% of its value since its most recent high (a bear market is generally defined as a loss greater than 20%):
On the other hand, the first appearance of Kara Zor-El in Action Comics #252 (1959) has been steadily rising in value during the same five-year period of time. Its value is up about 35% which easily beats the rest of the market:
Remarkably, if you were only looking at the value of this issue over the past five years, you wouldn't even know we were in a bear market since we don't see evidence of the comic boom (and subsequent bust) impacting the sales value of this issue over time. It's just been creeping up in value at a slow and steady pace like a tortoise.
Action Comics #252 is, of course, THE grail for Supergirl; however, as discussed above, it's not exactly cheap anymore. Earlier this year, this CGC 9.0 sold for a record setting $48,000:
Based upon recent sales, even a CGC 5.0 is going to set you back around $2,700. Speaking only for myself, that isn't affordable. And you'd also be purchasing this book at all time highs and working against the basic principle of buying low and selling high.
Supergirl's first solo story is an affordable Silver Age key.
Fortunately, there are many other great Supergirl key issues that are often forgotten about and are still affordable for many. For instance, I really love DC Adventure Comics #381 (1969) which is widely regarded as Supergirl's first solo story. You could purchase a high-grade copy of this late Silver Age key for only around $300. For example, this CGC 9.4 sold for $317 just a few months ago:
Action Comics #276 is an early Supergirl key issue with many first appearances.
Another great Silver Age Supergirl key is Action Comics #276 (1961). This issue, which tells a story about Supergirl’s first interaction with the Legion of Super-Heroes, is significant because it features many first appearances, including first appearances of Sun Boy, Phantom Girl, Triplicate Girl, Bouncing Boy, Shrinking Violet, and Brainiac 5. While these characters aren't exactly household names, with James Gunn's affinity for obscure characters, I wouldn't be surprised if some of them got some screen time in the future. This CGC 6.5 sold in June 2025 for only $264 which is a great price in my opinion for this Silver Age key that contains multiple first appearances:
Superman #123 features a "tryout" of Supergirl.
This early Silver Age key precedes Action Comics #252 and features a "Supergirl tryout" according to its CGC label. In this issue, Jimmy Olsen is granted three wishes and he uses this wish to create a woman who has Superman's powers. As you can see from this issue's cover below, she looks just like Supergirl! Sadly, this iteration of Supergirl dies, sacrificing her life by protecting Superman from kryptonite. As the CGC label suggests, DC was testing out the concept of a Supergirl with its readers before it created Kara Zor-El in Action Comics #252.
