As a new player, I'm noticing a lot of price manipulation of some key items. For example, the True Kathryne Keyron card used to sell for around 40m, but it appears that someone bought all of them and have bumped the price up to around 100m. Similarly, Rutilus-OS which sold for around 9m have been bumped up to 38m (or momentarily 100m at times). It probably doesn't impact the older players as much as the newer players, since it's the new players who don't yet have those equipments/items. As a new player, it's a negative experience to see this happening, since the system enables (and in a way encourages) this monopolizing behavior which is only possible for the already wealthy. It's a case of "the rich getting richer" and the poor dealing with more obstacles--which feels unfair.
The tax on >10m somewhat curbs the behavior, but it's not enough. I'm unsure of a good feasible solution to the monopolizing behavior, but I just thought I'd point out one of the negative experiences from my perspective as a newer player. Not sure if it's feasible to limit the reselling of equipments and cards, or if it's simply more feasible to set up alerts to monitor the behavior.
Note, to be clear, I'm not against reselling. I'm against monopolizing (or close to it) behavior.