I do wonder though when people try to sell used boots - maybe even customs - for $600 no matter how much they paid for them!
As a general rule, used skate and boots are worth less - but if the MK Dance
Blades weren't messed up by a bad sharpener, and they aren't warped they sell new for $500 list price, and about $465+shipping from discount stores. One could ask the seller which skate tech did the initial sharpening, and if is someone reputable, they might be worth close to that. Also, as of this writing, there are no bids yet - which means the seller might accept an offer for less.
If they are custom boots (which was not
stated - the statement that they are for people with wide toes and narrow heels is somewhat true of generic stock Harlicks), that likely just means they will probably fit fewer people than a stock boot would. The way I see it, for the most part, customs are not inherently better than stock boots, unless they are customized to YOUR body.
There may be some exceptions. At a fund raiser run by the Weiss family for their foundation, Michael Weiss's sister (one of his sisters??) told me that his boots had been very expensive (I think she said about $5000) because they used high quality materials and construction, presumably to cut weight or increase sturdiness? (I don't know if she was right.) I suppose it is possible that other high end skaters have had their boots customized in similar ways.
(It is always possible the blade shapes were customized too, by the skate tech - the seller might know - or refer you to the skate tech, who might know.)
If I wanted this type of boot and blade, and I lived near the seller (listed as Plano, Texas), I might be inclined to ask if I could take a look, and then maybe make an offer...