While finding and eliminating the underlying cause for your neck pain is the real key to preventing it from occurring again (by correcting your seated posture or removing stress from your life), there are a number of useful stopgap measures you can take to cure neck tension in the interim.
Most homeowners report spending between $3,675 and $7,155 to have air conditioning installed. This price is more typical of a central A/C unit installation rather than a window air conditioner addition which typically averages about $300. Your total cost for the job will depend on the type of system you choose.
If you have a bigger home with multiple rooms, you will probably need to have a central air conditioner installed. Homeowners can pay between $500 and $4,000 for central air conditioning. The final cost will depend on the unit, additional installation items such as ductwork and the professional's installation rates.