Have you looked at the power consumption of a TGV?
300+mph has been trialled, but the rolling stock suffered severe coning effects (look that up) which nearly resulted in the train oscillating off the track, the track, ballast, pantographs and (more importantly) the overhead wiring all suffered major damage and the energy consumption for the test rig (a short, specially modified train) precluded doing it on a normal TGV - most TGV sets are over 1/4 mile long and at these speeds on these kinds of trains most friction is on the sides of the carriages no matter how well polished they may be - the aerodynamics up front is primarily to ensure the nose of the train stays grounded and carriage lower fairings are more about stability than reducing friction. The practical limit for railed vehicles on conventional tracks seems to be about 250mph.
On top of that a TGV track is a very expensive piece of high precision heavy engineering with a roadbed going down 10-12 feet in most places and a very low tolerance for any kind of trash near the tracks (the winds generated by passing trains are severe and magnetic eddy currents from the motors will pick up and throw any loose bolts/nuts. FOD inspections are almost as rigorous as on airport runways and that means there's an (expensive) army of maintenance workers associated with TGVs compared with lower speed passenger lines.
The construction costs of Hyperloop are low by comparison, which mean that it can run a lot more places and offer greater frequency of service. On longer routes you can expect that pods will link up to form trains, so it won't be "1 pod whizzing past every 30 seconds", it'll be "20-30 entrained pods every so often" - which makes route switching and other logistics much easier to handle.
I really hope this works. If it does then shorthaul flying will be pretty much eliminated. As it is I much prefer to take the train (TGV) from my house near London to Paris/Amsterdam/Nice than to fly - and to Paris/Amsterdam the doorstep-to-doorstep time is usually significantly lower than trying to fly. To Nice it's longer - but far more comfortable.