I admit it, I have a soft spot for sports cards. Over the past year, an embarrassingly steady stream of small eBay packages have been arriving on my family’s doorstep in New Jersey thanks to my 12-year-old’s newfound love for basketball cards. As I think has become plainly apparent to my wife by now, I’m complicit in encouraging this passion—with more than a tinge of nostalgia driving my mind and heart back to my own baseball card obsession in the late ’80s and early ’90s. And I’m not alone. Trading cards like Pokémon and sports cards have exploded in popularity in recent years, fueled in part by nostalgic yearning during the early days of the pandemic and new digital gamification elements of the hobby that have turned collecting for some into an FOMO-induced, impulse-buying sport. Now, one of the fastest-growing startups in the space—New York City-based Courtyard—has raised a $30 million Series A to double down on growth. Forerunner Ventures is leading the round, joined by the company’s existing investors NEA and Y Combinator. Founded in 2021 by Nicolas le Jeune, who previously worked at YouTube, and Paulin Andurand, a former Apple software engineer, Courtyard markets itself through its website as selling “mystery packs” of cards and comic books via a digital vending machine. What that means in practice is that customers agree to pay either $25, $50, or even $100 for an unknown Pokemon or sports card—or $200 in the case of a comic book—and then an algorithm randomly assigns them a card or comic from the startup’s massive inventory of collectibles stored in the company’s secure vault. Before purchasing, customers can view the probability that they will “pull,” in industry speak, a card of certain value.If you’re disappointed by the card you receive, you have a few options. Courtyard will immediately purchase the card back for 90% of its fair market value. Customers can also choose to list the item for sale on Courtyard’s marketplace, which doesn’t charge any fees to sellers. That ability to quickly sell out of a purchase you aren’t interested in, or disappointed by, is at the heart of Forerunner’s attraction to the startup.“Courtyard stands out as the first collectibles marketplace that’s actually designed to be liquid,” Forerunner partner Nicole Johnson wrote in an email to Fortune. “That might sound like a small thing, but it’s a big unlock: it lowers the barrier to entry [for consumers] in a category that’s historically been tough to navigate.”If the card’s a keeper, customers can keep it secured for free in Courtyard’s storage facility, and have it shipped to them. (Many customers don’t realize, and don’t really need to, that they are in reality purchasing an NFT, or digital token, that represents a specific physical card—or piece of merchandise.) The mystery packs have been a hit. In January of 2024, Courtyard was selling about $50,000 of merchandise a month. Today—just a year and a half later—le Jeune says the company is selling $50 million a month. And that’s with the comic book category just recently launching and with all sales happening via a website; the startup is expected to release its first mobile app in the coming days. The startup makes money when it buys cards back from customers for 90% of its value and resells it to customers in a new mystery pack. The same card is sold an average of eight times a month on the platform, the company said. Courtyard also relies on a large network of collectibles dealers who source merchandise for the startup, helping make the startup the largest buyer of trading cards in the world right now, according to le Jeune.But clones are popping up and the CEO said he is willing to go into the red to step on the gas and expand the startup’s lead, through a mix of hiring, paid marketing, and product category expansion.“We want to make sure we double down on the growth and capture the market as fast as possible,” the CEO said.When I tried out the service recently, I purchased a $25 mystery basketball card. It turned out to be a rookie card for Jalen Green, a young NBA player drafted as the 2nd pick in the 2021 NBA draft by the Houston Rockets. Green was recently traded by the Houston Rockets to the Phoenix Suns and has not lived up to his initial promise. Courtyard offered me $9 for a card valued in the broader basketball card market at $10. I didn’t accept, and have chosen to store the card with Courtyard for now, hoping that Green might play better this year and the value of the card might increase, making it worth it to keep or to add to my son’s collection. For a first experience, though, it was a bit disappointing even if I knew logically that pulling a card of greater value was not at all guaranteed.I asked le Jeune about the risk that a first-time buyer experience like mine might dissuade a customer from sticking around and making another purchase.“We could fake it and make you feel at the beginning like you get a good card every single time,” he said, “but we would not be okay with that.”As the company gets bigger, he added, Courtyard will be able to offer more value to its customers for each transaction.“We grew so fast but it’s still the early days,” le Jeune said, “and there’s so much room to make it a much better experience.”See you tomorrow,Jason Del ReyX: @delreyEmail: jason.delrey@fortune.comSubmit a deal for the Term Sheet newsletter here.Joey Abrams curated the deals section of today’s newsletter. Subscribe here.This story was originally featured on Fortune.com