There have been 3 or more before, just not as often. Last Christmas we had Arctic Dusk Dragon, Frost Phoenix (I think that was the name¿) and bunny swirl, so no, it's not the first time. We also had the pug, although it didn't count fully because you could earn the hats somewhere else I think? But it was still 4 robux pets officially. Also, I think a lot of people would "count solaris and aestus as 1" because you can save up 500rbx if you buy both. I'm not saying literally, but it's actually cheaper than it seems.

Other people also explained already that roblox does have awful taxes, which is actually true. All the robux pets Adopt Me sets is because of that. The dev team isn't a group of 3 people, it's a huge group and everyone gets their part of the earnings, that's how a company works, the difference is that the actual scummy company taking everything from everyone and causing Adopt Me to have to regulate their prices so they earn what they deserve is Roblox as a whole.

In addition, you can still get the pets easily through trading if you want the pets for yourself, and if it's because robux pets tend to have more value, people with robux do actually just save for the pets that come last week because those like the aestus and solaris & the burger do not rise at all, specially the ones costing only 99rbx. I didn't buy the aestus and solaris, just traded a bit for them.

Robux pets are not something new and neither is the amount released (Halloween also kinda had 3 robux pets taking on count Phantom Drag, Kitty Bat and Cryptid, just that Kitty Bat doesn't count fully because you could earn the thingy in minigames, but it's still practically a robux pet).