Hello Jaysun, I don't know for sure if I understand you post correctly. But I think it is about crystals which are cheaper than the specific crystals for your transmitter.
That's right, and logical, most manufacturers of transmitters/receivers also make there own crystal (except for Synthesizer and Spectrum, but that's an other story). And the crystals of the manufacturer itself are (normally) better than crystal of another or "no" manufacturer. This is because the crystals of the manufacturer itself are specific calibrated for that brand of transmitter/receiver. So it is possible that with another brand of crystals the receiver/transmitter wont work properly, or that you will have lots of glitches. So I recommend to buy the manufacturers own crystals. Although they are more expensive. When having a glitch and breaking something you should already pay more money than without that glitch and the broken parts. Furthermore it is not a nice way to race when you know you've got a big chance of getting a glitch.