This is a great topic and one that is likely to have a large range of views.
I bought a 2014 in July and my mods to date have been limited to a xmitter light in the bumper, paint for bumpers and wheel arches, deaver +2's, SVC bump stop kit, K40 radar/laser detector and NTV for the Nav & Cameras.
My truck is my daily driver and I drive about 150 miles per day. I also will use it to tow our boat, tow motorcycle/quad trailer and for weekend off road excursions and of course to slepp my son back and forth to baseball and hockey games and tournaments. So it can and will do it all.
Here is how I would rate my mods to date:
The paint makes the truck look how I like it, so well worth the $1,000. 10 out of 10
The light works well offroad, so for those occasions it is nice to have and on the open road with no traffic is nice also. This was $1,200 - 6 out of 10.
The Deaver +2's were added hoping for a better ride and to carry trailer tongue weight better. I was able to custom order to address that specific issue. On ride quality they are better than stock in some cases and worse in others. In terms of carrying tongue weight they do what they were targeted to do. The other benefit is it improves the offroad ride. This was about $1,500 - 7 out of 10.
SVC bump stop kit and frame support - this showed its benefits on my first off road trip. I am sure it helped me out in hard running situations offroad. This is a mod I think is good to have and adds to my truck but not something I need everyday. This was about $2,500 - 5 out of 10.
The K40 came out of another car I sold, so it was easy to decide to add it to the truck. This is a very useful mod everyday. Cost $200 - 10 out of 10.
Ntv - this allows me to use the front or rear camera at anytime and allows me to use the key pad on the navigation while underway, instead of being limited to the voice commands. Being able to que up either camera at the touch of a button in any situation is a very nice feature. You can do it while running or when stopped. You can use the front camera for parking and the rear to see what is up with your trailer. This was $550 - 10 out of 10.
I enjoy all the mods and find the things I can use or see everyday are the mods that I like the best and add the most value to me. Having a "project" is a big part of our mod culture.
I have modded more trucks, cars, boats, moto's, quad's etc.. then I care to admit. I used to find myself modding things for the sake of modding. But now I find myself modding for their specific purpose with the focus on safety and reliabily first.
I have gotten better as I have gotten older in resisting mods that are cool, but really don't benefit my specific use or needs. The Raptor is a great truck out of the box, but it is fun to personalize it to you and your specific needs.
I have also learned to do all the mods when your vehicle is new (or as quick as you can) so you get to enjoy them all for the life of the vehicle. This helps with perceived value equation!
So the value of the mods for me comes from having a project, personalizing my truck and optimizing it for my needs. But as noted above the best part of the mods comes when using your equipment, whatever it is as often as possible with friends and family - that is where the real value is - the fun times and memories you create along the way are what you will remember!