It all depends on what you mean by 'macro' and 'lens'.
Reaching 1:1 isn't hard and needn't be expensive. The lens options:
1) New or used AF macro lens -- not cheap, and you don't really need or want AF for macro work, but good for portrait and short-tele work as well as macro.
2) Used A-type MF macro lens -- still not cheap, but you can easily use flash.
3) Anything else -- can be cheap, even VERY cheap, but flash is tricky. EXCEPT...
4) Closeup adapters -- very-to-fairly cheap, and you keep full AF and aperture control.
For (1) and (2), the 'dedicated' macro lenses with auto-aperture control, you gotta pay. Others here will suggest various lenses. With (4), simple uncorrected meniscus +dioptre closeup adapters are cheap but not real good; but corrected adapters can give brilliant results. The Raynox DCR-250 (about US$60) reaches 1:1 on a lens at about 200mm IIRC.
That leaves (3) everything else. Using flash is tricky without an AF or other A-type (auto aperture) lens. One cheap option is to use A-type macro tubes on your AF lens. Those may be hard to find, and not cheap. But A-type teleconverters ARE fairly cheap, and their glass can be removed, and you retain aperture automation and thus flash support. These are usually about 25mm thick, so two of them on a 50mm AF lens puts you at 1:1. This is probably the cheapest way to do clean macro.
If you don't need flash, you can buy a non-A-type MF macro lens. Still not cheap. Or you can use simple cheap extension (tubes and/or bellows). You can reverse a lens -- but reversal just brings you close (working distance about 45mm); you still need some extension to gain magnification. You can reverse-stack lenses and gain great magnification. But reversing or stacking primes ALWAYS puts you at that same close working distance. Good for studio work; not so good for the field.
You can reverse a zoom. DA lenses lack aperture rings, won't do. But any FA or F or MF zoom can be reversed, with a working distance somewhere around 1.3-2x the focal length. Even a lousy zoom, reversed, can give good results. Be sure to make a hood for any reversed lens. Macro tube sections work welll as hoods.
You can put a prime on extension. An Industar-50/3.5 on 50mm of cheap M42 tubes with a safe cheap flanged M42-PK adapter puts you at 1:1 for under US$50. For not much more, is my favorite: cheap bellows and tubes mounting cheap enlarger lenses. Use a 50mm EL for close studio work; 75mm for slight further macro work, and portraits; 90-110mm for portraits, and ahort-tele and moderate macro work; and 140-200mm for even more distance. I buy such EL's for under US$10 usually, sometime four for a dime, maybe as much as US$20 for a Leitz or Nikkor. EL's have edge-to-edge flatfield sharpness; they need hoods to avoid flare; they are FUN!
Feel free to ask for details.
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EDIT: I am rewriting this as an article on CHEAP MACRO. Corrections are welcome.