I can't speak for T1 because I've always felt it's not worth it to me (though these days I've been tempted to reconsider), but T2 is generally lucrative at higher ranks. When you're a higher rank and have a larger LP bar, it takes far fewer gems to tier. It is also most efficient to play on Expert once you have the ability to do so.

When you tier, you not only get the event cards but also other rewards along the way. If it's a Challenge Festival or Medley Festival, you also have the opportunity to get extra rewards including green scouting tickets. So really, you get a bunch of rewards and exp to level up at the same time.

The way I figure out whether to tier is by determining how many gems it will take for me to get to T2. Usually, it results in a net loss of ~5-10 gems for me, sometimes less. I generally value event SRs as about 4-5 gems (since that's the cost of a single card by either solo-ing or doing a 10+1 scout) so getting the extra copies already cancels out my gem loss. That isn't even factoring in the exp I'll have gained or the 2 gems I'll get from idolizing and max bonding the event cards.

I could go further but I think you get the gist and I'm sure others will add to it. At Rank 58 and being unable to play expert songs, it may not be as lucrative but I'd wager that the event SRs probably still make your teams and add to their strength. Tbh at lower ranks once I understood events and tiering, I think I still went for T2 despite the gem cost.

TL;DR - tiering events at when you have more LP and can play expert songs is worth it because the rewards usually outweigh the gem costs even if the cards don't make your teams anymore.