Hi :) want to take a train from Chengdu to HK .. Anybody had any idea how much it cost?

No, there is no direct train from Chengdu to HK, so I suggest you make a transfer in Guangzhou.
In Chengdu East Railway Station to take a bullet train to Guangzhou South, and the travel time is about 14 hours, the fare is CNY816.5 for the second class seat and CNY1,164 for the first class seat.
Then take the subway line 2 from the south railway station to Gongyuanqian Station, where you can transfer to line 1 to East Railway Station, where you can take another train to HK. The train fare is HKD190.

Well, the train cost is not cheap. You can also fly to HK directly. Or to save money, fly to Shenzhen, then take airport shuttle bus 330 to Luohu, pass the border and reach HK by metro.