Value-adds are, by definition, value added to an advertising schedule.
But how valuable are they to the overall media buy? 
Examples include remotes (radio), program and/or event sponsorship (“Brought to you by…”), free overnights, a booth at the local garden show, on-air credits (“mentions”), etc. In print, it could be a color ad for the B&W rate.
There’s definitely value in these add-ons. But, if they’re offered as part of a media outlet’s advertising proposal, the value-adds should deliver at least some real value to the performance of your campaign.
Here’s an example. A typical value-add for television and radio is the addition of a few extra ads overnight. Granted, there is some audience that listens to the radio from midnight to 6:00 am, but it’s likely a small audience and may not be the one you want to reach with your advertisements.
An important consideration with value-adds is that they should not be factored into your average rate with that media outlet.
Say the buy includes 10 ads at an average rate of $30, and there are 10 free ads thrown in. On the surface it seems to have brought the average rate per ad down to $15, but what are you really getting out of those 10 free ads? Placement matters. If the free ads are running midnight-6:00 am, is your target customer up and tuned in during those hours?
In television, appearance of a business along with the words “Sponsored by” have proven to be quite effective in advertising at the local level, while remotes for radio advertisers have been successful for local businesses such as retail, restaurants/bars/nightclubs, and automotive.
Another common value-add for print or broadcast buys is the placement of an ad on the station or publication’s website. One great benefit of this one is that it can increase exposure of your ad, reaching the busy mom that reads the newspaper online but not in print, or the college student that visits a radio station’s website for local band listings but otherwise listens to satellite radio and MP3s.
So yes, value-adds are definitely valuable, but just how much value they offer depends on how appropriate they are for your target audience and campaign goals.