Regarding the differences between the 24 and the 24C it is mainly in the tuning of the trigger and the fact that the 24 is a curved trigger, while the 24C is a flat trigger with the addition of the 'hipershoe'.
Which in theory the 'shoe' with its 5 positions on the back of the trigger blade give the user more customisable pull weight in addition to the 3 sets of springs (they reckon it gives 15 distinct trigger pull weights) To be honest i went straight for the 2lb springs with the 'shoe' on the lowest setting to get the lightest possible combination, i have since removed the shoe so i can get even further down the trigger. I prefer it that way.
The real difference is in the pre travel/creep and break of the triggers. The 24C (before the release of the 24-3G and the ECL) was the companies flagship trigger boasting no or no perceptible pre-travel/creep and a super crisp break with short reset.
All the Hiperfire triggers boast the impressive design which improves a lighter pull without sacrificing hammer fall energy (which is very heavy and useful with 22lr primers)
Here is a little write up from Hiperfire themselves regarding the differences...there are also videos on the website that explain the workings and differences.
Difference Between The HIPERTOUCH(R) 24, 24E, And 24C?
Hope this helps but to be honest i would spend the extra $50 and enjoy one of the top of the line AR-15 FCG's. The price you quoted is not bad they retail at $235 from the website and like the Geissele and Timney and other triggers they are not contracted out to china or other makers so i think you can be assured that it will be a genuine product.