Trading and getting sci data from events are not mutually exclusive activities before or after an event ends. They don't occur periodically either to be predicted or used as part of a plan to get money. If anything, too much is being pumped into the system that winners can hold onto them without a further need to trade since someone else will do it to buy off their data.
The only reason its problematic is because there is nowhere to spend money, so you can easily be set for cash after 1-2 events. The problem still remains even if you spent a few hours grinding out the cash through conventional means. People still stop trading/missions/mining after they have enough and honestly making 1bil a day is pretty easy for a vet. Ultimately there isn't really a net effect on the economy since the credits to buy data still need to come from somewhere, which still means it has failed at its job as a moneysink.
To make them an effective moneysink, sci data needs to be equally accessible to everyone (in the sense of consistency, no factoring in of ping, timezones, glorified unique wrecks like derelicts, etc), be locked to each individual player/ship and an increase in value proportionate to the economy.