How the advertised price works
Large national franchises lead with a low headline number to win the click and the call. The advertised $99–$129 generally covers a limited number of vents on a single system. Additional supply vents, return vents, second systems, sanitizing, and certain equipment all carry separate charges that are added during or after the visit.
There's nothing inherently wrong with itemized pricing — but it makes the real cost hard to know before someone is standing in your home, which is where the pressure to add on happens.
How flat-rate local pricing compares
A local contractor that quotes the whole job up front removes that uncertainty. You know the total before scheduling, the technician has no incentive to inflate the vent count, and the price covers the full system — supply lines, returns, air handler, coil, and blower.
Tampa Duct Cleaners charges a flat $624 per HVAC system — all-inclusive and quoted in writing before we schedule. No per-vent fees, no arrival-time add-ons, and Hales Comfort Club members save 20%. You know the full cost in advance.