I'm planning to do a trip to Longmen caves and White Horse Temple this week from Xi'an.

The bullet train from Xian North to Longmen takes 1h 30 minutes- 2 hours and CNY174.5 for a first class seat, CNY279.5 for a second one.
The taxi from Longmen Station to the caves costs around CNY15.
The taxi from the caves to the temple costs CNY50-60. Or you can take bus 53 and transfer to bus 56 at Zhongzhou Zhonglu Dingding Lukou. Get off at Baimasi, and it takes about 1h 30 minutes and CNY2.
The ticket of the caves costs CNY100; and for the temple costs CNY35.
As for hotel, you can stay in Luoyang Xiaozhen Hotel near the temple, which costs about CNY100 for a night.
So the total fare may be CNY400-600.