The payment standard and rent reasonableness are two separate tests, and a unit has to clear both. The $1,450 governs how the subsidy is calculated. Rent reasonableness is a finding that your contract rent is no higher than what comparable unassisted units in the same market command, and the authority has to make that finding before it executes a contract and again whenever you request an increase. $1,275 is their reading of their comp set, not a program ceiling.
Submitting your own comparables is usually worth doing, and the reason is that most authorities are working from whatever data source they subscribe to, which tends to lag and tends to be weak on unit-level condition. If your $1,500 comp across the street has one bath and yours has one and a half, or yours has in-unit laundry and theirs doesn't, that's the argument. Ask the authority in writing what comps they used and what adjustments they applied. Procedures for challenging a determination differ by authority, so get theirs in writing rather than assuming.
On the utility allowance: if the tenant pays gas and electric, gross rent is your contract rent plus the published allowance, and it's gross rent that gets measured against the payment standard. So $1,450 was never all available to you as contract rent. If the allowance is $120, your practical top end is closer to $1,330 before the reasonableness question even comes up.
An accepted comp set doesn't automatically travel to the next unit, though in practice an authority that already accepted your evidence on unit 1 tends to move faster on unit 2 in the same building.
The thing that costs more than the spread is abatement. If a re-inspection fails and payments get held, you're carrying the unit with no voucher income and a tenant still in place, and that erases a year of the $6,000 you're chasing.