Haha... just go for the cheapest plan, even if the 10gbps is the cheapest.
Different people may have different interpretation of what is the "cheapest" though.
1. Usually I will cater in the price of the bundled router (estimated price if selling in Carousell) and calculate the effective price.
Some power users will want to use their own router and then sell the bundled router. Some users will want to reuse the existing router and then sell the bundled router to offset the monthly price.
The above method suits these two group of users.
In this case, 6Gbps plan may be the cheapest.
3Gbps at S$32.90 per month, minus S$72/24 = S$3 (assuming selling the bundled router for S$72), effective price at S$29.90 per month for M1 3Gbps without router.
6Gbps at S$38.90 per month, minus S$288/24 = S$3 (assuming selling the bundled router for S$288), effective price at S$26.90 per month for M1 6Gbps plan without router.
10Gbps at S$30.90 per month (Christmas offer) --> effective price at S$30.90 per month for M1 6Gbps plan without router.
6Gbps may be cheaper than 3Gbps in this case. As for 6Gbps versus 10Gbps, it depends on how users consider the extra 2.5Gbps bandwidth is worth the extra S$4 or not. I will say no.
In this case, 6Gbps plan is the way to go.
2. Many average users will use whatever the router the ISP gives and they are afraid of plans without a router. They may not understand the differences among TP-Link Archer BE230, Asus RT-BE58U, Asus RT-BE92U and TP-Link Archer BE805.
This is probably why SIMBA starts to bundle a low end D-Link router for its 10Gbps plan. WC also puts more focus on the router bundled 10Gbps plan now, even though they bundle lower end 2.5Gbe capable router only (but they do mention wired speed is only up to 2.5Gbps for Archer BE400 or Deco BE25).
In that case, they will think 3Gbps plan is the cheapest at S$32.90 per month, 6Gbps is the next at S$38.90 per month, 10Gbps is at S$39.90 (Christmas offer plus top-up of S$9 for Asus RT-BE92U) or S$40.90 per month (Christmas offer top-up of S$10 for Asus Archer BE805).
3. Yet another group of users just look at the monthly price without looking at the details at all. They will be very happy with the S$30.90 10Gbps plan since it looks to be the cheapest.