A bounty of ten thousand Spirit Stones for a Gu Cultivator in the Out-of-Dust Phase; the price... hard to say, but definitely not high.
Like the first Out-of-Dust Phase Cultivator Feng Jun killed, Yu Meiren, this person's entire wealth amounted to just a few thousand Spirit Stones. If not accounting for the Immortal Binding Rope on him, one could almost consider him dirt poor. Expecting to kill him for ten thousand Spirit Stones was practically a dream.
Normally, Cultivators expect no less than eight thousand Spirit Stones for killing someone in the Out-of-Dust Phase—equivalent to the price of two Magic Artifacts.
Gu Cultivators are not only tricky but notoriously difficult to deal with, so a bounty of ten thousand Spirit Stones to eliminate a Gu Cultivator in Out-of-Dust Phase really isn't very appealing.
Thus, when the Chu Family issued the bounty, they made the cause and effect clear—had they not, even Tiantong might not have accepted this job.