In my mind, competitive is a tag that validly states that you are trying to go absolutely to the extreme of making the deck better at any cost. Tags of percentage don't contain any information like that. Something like Budget often dictates that suggesting cards that cost > $10 likely aren't an option and I think that is a valid tag as well.
I just don't see what these kind of tags would really give to readers.
This is sort of valid. There's only so much information a tag with a single phrase or statement can convey. It's no substitute for actually reading a thread.