Honestly I admit I missed the boat:
Poloniex had no fees
Starting from October 21, 2019 17:00 UTC, all spot trading fees will be reduced to 0.00% until December 31, 2019 23:59 UTC.
On top that, there is another promo: https://poloniex.com/leaderboard/trx-trading-competition
Why I bother? Arbitrage
I really wanted to do this, but unfortunately "all talk, no action" - I was busy with small potatoes rather significant potential gains...
It's essentially a magnet, something to get traders use the platform, use the bots, provide liquidity...
(now the boat has sailed - note to self - focus on bigger potatoes)