Curved hardwood stair treads are very popular right now.
How to install wood flooring on curved stairs.
This video has some great techniques and tools tips that will help you achieve tig.
Watch installing hardwood on stairs.
I cant see if the risers are curved as well if they arent then you could just cut the front of the stair square then install a square tread.
How to transform carpeted stairs into hardwood.
This would do all the stairs except maybe the bottom one that one looks like you would need a stair shop or.
Cost of installing or improving the subfloors.
I can see the stairs have a slight curve to them they may be hardwood under maybe not.
One of the most dramatic remodeling changes you can make is to rip up all the dusty old carpeting in a house and replace it with hardwood.
Things i mention in this vid.
How to install the first stair nosing.
Dewalt miter saw http amzn to 2i7jonf dewal.
If the existing stairs do not have a subfloor the floor under the flooring or if there is a problem with the quality of the subfloor then this should be addressed.
Either way those are ideas from the past.
You might have been told that it can be done but it will be very expensive.