First off the repairs will be around $1500.00 for just the airbag replacement and around $4000.00 plus if the dash is ruined as well.
You need to call the Lexus Customer Service Department and speak with them concerning this because from what you are saying this has been a problem while is was under warranty and what they can do for you is called "Good Will" meaning they can fix this for free to please the customer and they do it all the time.
Phone: 1-800-255-3987 Lexus Customer Service
Below is a list of (TSB) Technical Service Bulletin Titles for 2004 Lexus ES 330 V6-3.3L and many has issues concerning the Restraints and SRS Components.
TSB Number & Issue Date TSB Title
SSC4LI DEC 04 Recall - Seat Belt Status Switch Replacement
TSB Number & Issue Date TSB Title
LSC4LG NOV 04 Campaign - Navigation System DVD Update
TSB Number & Issue Date TSB Title
PG008-07 NOV 07 Vehicle - Replacement Certification Label Information
PG007-07 NOV 07 Vehicle - Replacement VIN Plate Information
SS006-07 AUG 07 Electrical - Absorbed Glass Mat (AGM Battery Information
SS005-07 AUG 07 Restraints - SRS Component Disposal
EL007R-05 AUG 07 Restraints - SRS/Air Bag OFF Lamps ON/DTC B1785
TC008-07 JUN 07 A/T - 'World Standard' Fluid Information
EG015-07 JUN 07 Engine Controls - Bank 1/Bank 2 O2 Sensor Identification
ST004R-01 MAR 07 Steering - Vehicle Pulling, Manual Supplement
TC002-07 MAR 07 Drivetrain - Driveshaft Replacement Precautions
SS002-07 MAR 07 Engine Controls - Techstream(R) ECU Flash Reprogramming
EL002-07 FEB 07 Air Bag System - Repair Manual Supplement
NV005-06 DEC 06 Body - Upper/Lower Windshield Ticking Noise
PG001R-06 NOV 06 Battery Maintenance for In-Stock Vehicles
EL010-06 SEP 06 Body - Rear Power Window(s) Inoperative
BO005R-06 SEP 06 Keyless Entry - Transmitter Key Casing Availability
PA003-03 JUL 06 Paint - 2004 Year Model OEM Paint Codes
NV001-06 MAY 06 Interior - Front Seat Squeaking Noise
AU001-06 APR 06 Audio System - Quick Reference Troubleshooting Guide
BO009R-04 DEC 05 Restraints - Seat Belt Extender Availability/Application
SS003-05 NOV 05 Audio System - CD Player Skip Verification
BO012-05 NOV 05 Interior/SRS - Seat Cover Replacement Recommendations
SS005R-01 AUG 05 Antitheft - Diagnostic Tester Immobilizer Function
BO004-05 JUL 05 Wipers/Washers - Wiper Blade Cleaning/Maintenance
EL009-05 JUN 05 A/C - Inoperative/A/C Light Flashing
EG012R-04 JUN 05 Engine Controls - Entering VIN After PCM Replacement
ST001-05 APR 05 Steering - Clunk/Pop/Knock Noise Turning
TC004R-03 APR 05 Engine/Transmission Controls - Poor A/T Shift Quality
EG007-05 MAR 05 Cooling System - Radiator Cap Inspection Procedure
EG006-05 MAR 05 Engine Controls - MIL ON/DTC P0346 Set
EL002-05 FEB 05 Restraints - Passenger Air Bag Lamp ON
EG003-05 FEB 05 Engine Controls - MIL ON/O2 Sensor DTC's Set
PA001-05 JAN 05 Paint - Iron Rust Contamination Repair
EG008R-04 JAN 05 Emissions - LEVII EVAP System Check For Multiple DTC's
BO012-04 DEC 04 Interior - Console Lid Lock Opener Improvement
AC005-04 DEC 04 A/C - Sensor Inspection Procedures
ST003R-04 DEC 04 Steering/Suspension - Vehicle Pull or Drift
EG011-04 OCT 04 Engine - Main Bearing Journal Diameter Stamping Revision
CRIB141 OCT 04 Paint - Chip Resistant Coatings
NV006-04 SEP 04 Interior - Squeaking Noise From Seat Track Area
EL007R-03 MAY 04 SRS - Occupant Sensor DTC's B1150 and B1650
NV004-04 MAY 04 Interior - Rear Door Trim Panel/Seal Rattles
TC003-04 APR 04 A/T -Transmission Solenoid Identification
PA001-04 APR 04 Paint - Color, Scratch Resistant & Anti-Acid Paint
BR001-04 MAR 04 Brakes/Traction Control - 'Zero Point Calibration'
ST003-04 FEB 04 Steering/Suspension - Vehicle Pulls to The Left
EL007R-03 DEC 03 SRS - Calibration of Occupancy Classification System
BO012-03 DEC 03 Interior - Seat Belt Extender Applications/Availability
NV011-03 OCT 03 Body/Interior - Rear Seat/Parcel Tray Area Rattles
SS003R-01 SEP 03 Engine Controls - ECU Programming Error Displayed
PA003-03 JUL 03 Paint - Paint Colors - All