If you're asking about price fluctuations on the prices of rs3 gp it's pretty much consistent, just a very gradual decline. Osrs is a different story obviously.
1 person shouldn't cause a panic. If they really did crack down on RWT, we would've seen lots of more threads on people getting banned or gold sellers giving us a warning.
Jagex bans people who sell sizable amounts of gold, and even then it's rarely ever instant. Buying gold has always been extremely low risk, and I would be damn surprised to see someone actually be banned solely for buying.
2011-2012 was an era where jagex nearly overlooked rwt, except on a massive scale (the users selling billions per day).
After 2013 Jagex really stepped up their game and has been banning loads more, I would say that ban rates are at least double what they were in previous years, maybe even higher.
I have lost 2 accounts, which is nothing. It's such a minimal chance to actually be banned for RWT'ing. Change your mules occasionally, change IP addresses, follow safe trading practices and you won't have any problems.