I'm researching/ investigating / designing an 8 string (extra D and G courses) guitar, and saw a tip in the archives that using 4 on a plate mandolin tuners let you keep a 6 string size peghead.

That sounded good, so off I go to Google mando tuners.

And I've got to be missing something, because why are Waverly 4 on a plate mando tuners $600+?
Their guitar tuners are $200-$250 for 6 - how does 8 tuners equal 3 times the price?

I'll be sticking to some econo-versions when I build this, for sure.

Because they can and do sell them for that that's why. Additionally the volume of sales of this product are substantially less than other Waverly tuners making them more expensive to produce.

Waverly is great stuff and for traditionalists it's very much in demand and likely always will be.

A related question is why do clients have to buy 6 tuners when only one failed. Same answer...

Do you have your heart set on open back tuners like on 4-on-a-plate tuners, or would you consider closed back tuners? Gotoh makes nice small body, small button tuners that fit nicely on my octave mandolin headstocks, which are identical to my guitar headstocks. If you are going for a traditional look, they won't be a good fit, but if a traditional look isn't what you need, Gotoh SGS510Z-AO7 tuners might work. The headstock below is 6" long from the nut to the tip and there's plenty of room for eight of these tuners and there's enough room between the buttons for easy tuning.

I get that.

Always liked waverly guitar tuners. I was just surprised at the difference.

I’m open to whatever - your stuff looks good. Thanks for the tip.