This is the best start you can hope for, which is why decks will almost always run 4 copies of Collector to maximize the odds of this
So far in 2020, we've been averaging about one per month (and if you go back to the initial release in December, we've actually had 13 individual drops in three months, making the average closer to four drops per month since the series was announced), although the average is somewhat complicated by how you count themes that come with multiple drops, like the original Theros Gods during Worlds in February (technically, the Gods were five individual but related drops, although there is an argument for counting them as one big drop since buying all of the drops together was an option)
For example: Sun & Moon Set Symbols are typically a sun or moon icon and Sword & Shield Sets use a sword and shield symbol
Urza's Bauble is one of only two cantrips in existence without any costs attached
Iono (Special Illustration Rare) 3
Gandalf the White ($12.98 Regular, $14.70 Showcase, $20.88 Borderless) Panharmonicon where Legends Matters on legs, enough said