Vortex Smart used to be a bit cheaper, but I guess has proved popular, and now it’s turbo-buying season. Max bargain at the moment seems to be the Flow Smart, only sold by Halfords and Decathlon. Seems to be a Vortex but with slightly lower max resistance. £199 at the mo in Halfords:
http://www.halfords.com/cycling/turbo-trainers/trainers/tacx-flow-t2240-smart-turbo-trainer
My Vortex has its limitations, but overall is pretty good. I find using TrainerRoad with it and a power meter good, but not perfect – the software cocks up pretty regularly. I *think* but am not sure, that the TR powermatch do offer attempts to regularly send recalibration signals to the turbo. These frequently don’t get through, and it all goes tits up. I’ve no idea why they don’t just leave the turbo’s internal calibration well alone and just do that all on the TR side, sending resistance requests in pseudowatts instead of watts.