As far as intentionally releasing significantly over powered champions for more money, we should see a pattern in the patch following a champion's release if that was true, with over powered champions being nerfed and under powered champions being buffed. With that as our measuring stick, lets look at the wiki (and PBE for Ekko) to see who falls in what category.
- Ekko's OP
- Bard's UP
- Rek'sai OP
- Kalista slightly UP (more or less a wash of buffs and nerfs, but the Rend buff seems slightly stronger than the nerfs)
- Azir should have been delayed another month (UP because everything broke?)
- Gnar was UP
- Braum was OP
- Vel'koz was balanced
- Yasuo was balanced (only nerf was to Statikk Shiv interaction with his passive)
- Jinx was OP
So of the last 10 champions to be released, only four were released over powered in more than a year's time. The balance between OP and UP champions is the same for the most recent five as it is for the least recent five, which implies that things haven't gotten any worse.
I'm citing the Wiki for all of this so that personal memory of things doesn't bias things. If you can do the same we could carry on a discussion about it.