Roxi,
Don't be afraid to be creative...
I have some "formal" Stairs, but as you have seen they are pretty expensive. But in other instances, I use a Cardboard Box to a Chair, to a End Table to the Window Seal, to get my Male Yorkie where he can see out the Window.
Sometimes, just re-arranging the Furniture can get
the job done.
I've found that they don't mind a more "complex" route, as long as they
can get where they want.
Have a good Day !
S.W.