Yeah and you really want to spend all that money for a trip to bathurst
Right, looky here.
For a SYD-BHS-SYD daytrip, you have two options. Option number one: Dubbo XPT. Departs Sydney Central 0710, arrives Bathurst 1043; departs Bathurst 1707, arrives Sydney Central 2049. The timing is perfect for a daytrip, giving you six hours and a bit of time in Bathurst; you travel in reasonable comfort.
If you're too much of a cheapskate to cough up for that, here's option number two: you can have a cup of concrete and take the CityRail service. This consists of an electric interurban to Lithgow, connecting to a coach onwards to Bathurst. There are several such services daily, so take your pick.
If you really, really
want a CityRail day train, start a campaign for it and put your heart into it. You never know, you might see it made reality one day. Right now, you have two options: convenience and comfort, or cheapness. Take your pick.
Cough up, harden up or stand up. Your choice.