Going back to the original post. What are you intending to make, what material requirements, what precision? If you product quality is particularly high and demands a correspondingly high operating cost, than perhaps reconsider your budget.
The most precision demanding lathe project I had completed was during my apprenticeship at McGill. A remote manipulator arm in a vacuum chamber for inorganic chem. Sorry no photos. Multiple shaft largest of which was 50mm dia, 300mm long. 10-20um dia tolerance window, double that in length requirements between shoulders, 316 ss. For this requirement, all measuring tools and DRO were 1um reading. Hardinge and Mazak machines. Iscar and Sandvik cutting tools. Well over a million dollars in the listed tools and machines. You can make due with cheaper tools and machines and get similar results. Though there are so many variables floating over your heard already that having to fight your machines just to cut a straight line and remembering compensation factors in your tools just destroys your productivity and makes your scrap pile out weigh your products. Basically the story of my home shop.
You mention 303ss and 4140. 303 is fantastic as it machines like mild steel and is stainless, though is difficult to get hold of in the required size or shape, lacks the strength and corrosion resistance of 304 and 316, and can't be welded as effectively those. 303 is always soft, 316 is always hard, and 304 is soft when you don't want it to be and hard when you don't want it. 4140 and other high tensile along with tool steels, are all very costly on tool life as given, though are also particularly demanding of rigidity, torque and hp. Tool deflection destroy your finish and tolerance, large diameter parts can at times need more torque to make a chip than the spindle can provide. Hp is needed not only for productivity though to form a blue chip. Counter intuitively, like how an air craft needing less fuel per mile when going super sonic than transonic, machining to a blue chip needs less power and prolongs tool life than a silver or gold chip.
Long story short. a Logan 210 and Hardinge HLV have the same swing and distance between centers, also equivalent chuck and tool capacity. The major difference is that the castings are 4x the mass, and motor is 3hp and not 3/4hp. For precision parts in tough metals these are necessity, even if the ways and bearings are equally straight and round.
The Masturn 54-800 at work is the greatest lathe I have ever run. The capacity and precision as a combo are unmatched. Though it was +100k$ in 2004 dollars. A Haas Tl-1 would be the modern equivocation in a smaller form factor. CNC is a big jump in price, but the capability of complex shapes and production runs make it indispensable even in a prototype environment.
