When a druid or ranger casts revivify, it uses up 300 gp worth of specially gathered mistletoe berries. For details, check any version of the spells document. You can find such berries in Courageous Cape, up to seven at that price.

If you are interested in gathering your own, you will need a special mithral sickle (1000 gp), and solstice. While one of those is happening soon, you would need to be in the southern hemisphere- basically you would need to make a plan of that.

In the meantime, bully the group into splitting the cost of this vital component if you plan to prepare the spell at all.

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In core 5.0, druids do not have revivify. It is an optional extra spell for them in Tasha's, which is why it is on a lot of online spell lists, but not all of them. The different spell component is my change because it is stupid for you to have to mine a fucking diamond. Otjer fun facts:
Artificers, Dark Knights, Paladins, and Rangers can prepare it starting at level 9, as their casting progression is half of the full casters.
Divine Soul Sorcerers can learn it at 5th, but it is a pretty spendy pick for that class.
Celestial Warlocks can take it at 5th as well, but for them it is a last resort- warlocks have so few spell slots (2-3 for most of the game) that it will either not be available when needed, or the warlock will give up a lot of his normal spell play.
Lore bards can cast it starting at 6th, and all bards starting at 10th. This is one of the best uses for magical secrets if the party otherwise lacks it, but magical secrets is am incredibly powerful and scarce build resource.

I feel like you said it was warmish. So it needs to be the winter solstice?

Yes. The winter solstice is also the summer solstice if you willing to travel a lot though.

I feel like we should be fine with splitting the cost of a few clumps of berries, at least for now. Then again, I worry when the DM is so laser-focused on telling us about a spell to revive PCs. Maybe the clumps first, and the sickle later if we find ourselves casting this a lot?

It has been months since character generation, which is likely the last time you really dug into the spells document and the (now slightly out of date) diffs document. It is entirely possible that you forgot that druids even have revivify. Also since you have never cast it in 5e you may be unaware that it is one of the rare spells with an expensive component you must buy ahead of time- something very few druid spells have. Also someone is gonna walk just straight into lava at some point I promise.

No, I actually recently noticed that I get Revivify, mostly because we now have 3rd level spells. But it didn't seem out of the ordinary, mostly because I'm not super familiar with all of the "who gets what" nuances of the standard rules, and I just noticed it in the set of spells you gave us and all seemed fine.

BUT, I didn't realize it had the expensive component. Although it makes sense because of the "hey, you're now alive again" spells all have expensive components.

Yeah, but there's a 94% chance it's the druid.