A talkbox might seem like a needless extravagance to you. An over-priced relic of days gone by that will make your guitar sound like its stuck down a drain.
Well, yeah, it's expensive, but like the MXR Variphase variable phaser, it's the sort of luxury item that's well worth shopping around for.
This is a truly inimitable effect. Just consider classic tracks like Kickstart My Heart, Sweet Emotion or Living On A Prayer – the Talk Box was conversant with all of them.
Sadly, you'll need to play through a PA to use it, but if you do, you'll find an excuse to make the most of it whenever you can.