Hi guys. Chris here, from Apogee. I happened across your great posts and wanted to add a little info. The new 500 series PAR meters we just released have a different sensor head that has a new detector that was over two years in development. It's not just a recalibration of the old meter. For the upgrade special we're running right now, we actually take off the old black sensor head and replace it with the new head. We're able to re-use the old meter, although we do upgrade the firmware. We also credit you for turning in the old head so that also saves a little. We're running this limited-time, super deep discount as a way to build awareness of the new 500 line. We've had a huge response and we may be cutting it off very soon, so I'd jump in now if you're interested.
As far as discounting our MQ-200 meter, I doubt that will happen since we still have a strong demand for it among horticulturists that use Metal Halide and CFLs, etc.
Also, and this is a little preliminary, we should be releasing a USB version of our new 500 series PAR sensor (it hooks straight to your computer without a meter) later this Month (March 2016). We're putting the final touches on the software. The US retail price should be about $395, so keep an eye out for that. If you guys have any questions, I'll try to keep an eye on this forum, or feel free to email our tech support or sales departments. Thanks!