Singtel is usually charging the highest price for the plan. It is now charging S$137.72 per month with free GT-AX11000 Pro (Singtel claims that it is worth S$759, and indeed Challenger is selling GT-AX11000 Pro at S$759). So S$138 may be the ceiling price for the 10Gbps plan.
Starhub is giving an all-in-one ONR, or you can top up for TP-Link Archer AXE300 at S$7 per month (total S$76.3 per month, with free Premier+ (Premier League) for 24 months, Disney+ and Viu Premium for 12 months).
Basically Starhub is charging similar price to the 2Gbps plan (dual 1Gbps plan) for UltraSpeed trial. After all, Starhub mentioned the following in their FAQ.
https://www.starhub.com/personal/support/article.html?id=kD5GRQtfxB3LxaEDMjuFm5UltraSpeed is a 2Gbps broadband plan with a 10Gbps broadband trial to give customers an extra speed boost. We hope to continue the delivery of up to 10X the speed of 1Gbps Fibre Broadband after the trial, subject to regulatory approvals.