I don't really think it's necessary. There aren't a vast array if choices. Each job only has one item per slot for each currency anyway, so often times an upgrade is an upgrade. You are also given the ability to try the item on and also compare stats to what you currently have. You should be able to make an informed decision on purchases. I can't imagine that buyer's remorse is such a huge problem that we néed a refund system. If it is, then players just need to take more responsibility for their decision making.