IDK about 15m for segments because I've never seen anything like that before and that sounds crazy. But a midboss clear for 2-3m is fairly common. Especially if it's for an off job you are just gearing on the side.
I have formed PUG dynamis midboss clears that took around an hour to just get to the statue and down it. Sometimes it's easier to just buy the clear. 3 days of Odyssey and it's paid for.
Kudos for offering a freebie.
Not sure if i'm spelling the name correctly but someone named Alunes offered 15m for 3k segs not too long ago (obviously gilbuyer)and wanted all T3 Ody bosses merced for 30m each too.
Day after that he/she wanted to buy 50k escha beads for 50m and was looking for full aeonic clear x2 for 60m.
Not sure if you the same Buukki as on Asura but you calling this "crazy" makes me think you're not on Asura or you would've seen him/her and other insane people offer hilarious amounts of gil for stupid stuff.
Edit: if you are infact on Asura, Alunes was just offering "anything" for VD Ambu and just found a seller for Kin where he will pay 20m for ->every<- drop.