I can meet you in the middle on "considerably less attractive" :-)

For what it's worth, if I wanted zero-cost then the way I'd probably write that in Common Lisp would be with a more spartan abstraction like:

  (deftype f () 'double-float)
  (deftype points () '(simple-array (2 *) f))

  (-> euclidian-distance (f f f f) f)
  (defun euclidian-distance (x1 y1 x2 y2)
    (sqrt (+ (expt (- x2 x1) 2) (expt (- y2 y1) 2))))

  (-> point@ (points integer) (values f f))
  (defun point@ (points i)
    (values (aref points 0 i)
            (aref points 1 i)))

I'll grant you that's a kludge compared with your example. It wouldn't hold me back though. And I wouldn't consider trading in my lovely late-bound programming environment for an issue of this magnitude.