As far as I know, membership prices and tiers/perks are set by the channel. But it's possible something could have changed in Youtube's conversion to whatever your local currency is.
It seems like $5 is settled as the "standard" for a VTuber membership, but it's possible to be higher or lower, and it surprises me that more indies/small corpos haven't been experimenting to see if there's something more optimal for them.
Before Beatani jumped the shark (for me at least), she had a $2 tier but made fun of people for joining that as opposed to the normal $5 tier. It was a good system that I guess would only work for kusogaki archetypes lol.
Also, shout out to actual angel Tokino Sora, who didn't have Youtube membership for the longest time because she didn't want to double-charge her fans on both Nico and Youtube. People wanted the green name in chat though (IIRC), so she eventually opened membership at $3/mo with no higher tiers.