Many of the vintage MAC knives are from the "Original" series. This series was intended as a set of knives for commercial kitchens - hence, the hole in the forward end of the blade, to hang the knife up after use and cleaning. The knives are stamped, machined steel with no metal bolsters, and the 9 inch blade chef's knife (14 inches overall length) is a good value for beginning a working collection. It is a very thin blade, which adds to the ease in cutting. Like all MAC knives, Original series knives will take and hold a good edge. For many western chefs, the Original series knives were their introduction to Japanese cutlery and their properties were a true revelation about the limitations of western knives.
The downside issues of the Original series knives are several: the thinness of the blade makes for a very flexible blade (not as flexible as a fish fillet knife, but fairly flexible nevertheless compared to heavy western knives. Many chefs prefer a stiffer blade than the Original series provides. There is no bolster, so the heels of the knives (there are several rounded indentations on the 9 inch chef's knife) may need to have their corners relieved (done with fine emery paper wrapped around a round dowel will do the trick easily enough). There's the tip - rounded, rather than pointed. And finally, the handle protrudes far enough forward as to make sharpening of the area near the heel difficult. It can be fixed - provided you use some woodworking fine saws and wood shop utility knives to relieve some of the forward part of the handles. Using a wood rasp also helps in rounding and relieving the forward end of the Original and Superior series knives. Just be careful not to saw, sand, cut or rasp too near to the forward rivet.
I have bought some of the Original series knives and can attest to both their quality and to their plainness.
You should be aware that all of the significantly used MAC knives I have bought needed sharpening - they were all DULL!
I have also bought slightly used higher level MAC's and there were usually some minor problems with them.
However, if bought cheaply enough (say under $30, including shipping), the MAC Original 9 inch blade (14 inch overall length) and then sharpened is a very good value knife. However, it needs to be compared to the value of a new Tojiro DP, a Fujiwara FKM or even an IKEA Damascus Slitbar.
Concerning knives being cheaper - while it might be true for stainless steel western knives, it won't be true of quality carbon steel knives. You will find that there's a lot of junk offered - especially mass market stainless steel knives whose owners never knew how to sharpen. Instead, they try to get rid of their existing dull and abused knives, so they will have room (and a feeling of a clear conscience) to buy a set of new knives. One way of thinking about it is that "Hope Springs Eternal" - uninformed sellers have overexpectations about their offerings. I don't necessarily attribute that to intentional fraud (though that does occur), but to general human expectations.
As Benuser pointed out, there are problems with good knives having undesired recurves and protruding bolsters whose previous owners never properly sharpened their knives. Knives can also be used so much that the edges are progressively sharpened so far back into the face of the knives that there are wedging issues. Can these knives be restored? Theoretically yes, but it often means that the blades have to be significantly thinned and bolsters significantly reduced - so much work that there's a real question as to whether it's worth it.
In fact, at this point, I am thinking that the initial money spent on a first really good quality knife might be better put towards a good cutting surface, a good honing rod (the 12 inch Idahone) and the beginnings of a good freehand sharpening kit.
(p.s. - "Galley Swiller" is because I was initially on a small cruising boat, hence "Galley" and much of what I produced could be considered as "swill". Hopefully, I will not try to take myself too seriously)