High-speed rail second-class seat 23 1, first-class seat 363, business seat 72 1.5.
2 yuan, the subway from Beijing Railway Station to Dongzhimen, should be around 25 when the airport is approaching the Capital Airport T3. I don't remember the details clearly.
There is no way to give you an accurate ticket price. The price is different every day. I suggest you check directly with Air China or HNA official website, or through Ctrip.
If you don't have to take the high-speed train, the earliest express train 12: 17 will arrive in Beijing. You can choose an earlier flight. If you care about the price and time, you can also choose a later flight which is cheaper.