actually no i don't think this holds, because it is always EV for the losing party to make a bribe proposal to the futarchy, even if the futarchy will probably reject it due to a counter-bribe from the winning party.
the losing party only pays if the futarchy accepts the bribe, but imposes a counter-bribe/defence cost on the winning party regardless.
Would attempted bribery of an equity value-maximising futarchy oracle into making false reports be structurally unprofitable, given the bribe can be symmetrically countered by the party harmed by the false report?
(Assuming the initial bribe is large enough to offset the false report’s effect on the futarchy’s reputation, hence expected future revenue, hence its equity price)