Again, there are many more dopaminergic terminals in a smaller volume in the striatum compared to the cortex. Therefore the dopamine transporter is probably much more rate-limiting in the striatum than in the cortex. In the cortex, diffusion is probably more important. The critical finding of this paper is that the transporter seems to have a different role than just removing transmitter from extracellular space. It seems to be controlling an enormous flux of dopamine through the neuron and thus contributing to the subsequent packaging and release of dopamine.
Current evidence suggests that synaptic vesicles are recycled quite fast.
In temperature sensitive drosophila mutants where you block the retrieval of vesicles, you can cause synapses to shut down in 2-3 minutes. That means all the vesicles are fused in 2-3 minutes. Therefore, all the dopamine has to be put back into vesicles in 2-3 minutes. Somehow the flux through that compartment has to result in packaging of practically all the dopamine back into vesicles. These calculations help us appreciate that steady state levels of dopamine in the cytoplasm are quite low, and therefore the flux of dopamine through the cell has to be enormous to keep up with synaptic transmission.