Easy answer is quite frankly most people do their own. If you take all of Aerotronic's and our output of completed RV panels along with a few other panel shops, the output of completed panels is but a drop in the bucket of yearly RV registrations. Aerotronics and us easily account for the majority of completed professionally built RV panels, but there are other shops (some come and gone) that have and continue to do some as well.
So, just by simple numbers it means that most builders do their own - either with our without assistance. That being said, if you have high $$ glass and lots of avionics in it, that is where you often times see the shops come in. The simple truth is most panels are not that complex, and a lot of the complex ones are done by the shops. But - you'll see some very complex panels done by individuals who do a great job, but you'll also see very simple panels done by shops. Aerotronics does a lot of the really high end fast glass stuff that we try to stay away from - as RV builders ourselves we like to stick with what we know and what we've built so obviously we do more RV panels than other types of planes (also just because there are more RV's than anything else being built).
Anyway, if you had/have a subscription to kitplanes you'll see that they have spent the last year (and more coming next year) on articles to help you do this yourself if you don't have the resources to do it yourself. Some say I'm being a bit dumb by writing these articles (some of my colleagues in the business have given me a little grief about it) telling you how to do your own panels and wiring, but the simple fact is that not every builder needs or can afford to have a panel professionally done.....so looking at it from my perspective many years ago when I was building my first RV, I sure as heck would have liked to have some pointers about the panel - because I had to learn it all the hard way! That's why the articles are there and will continue to be as long as I have my say.
It kind of comes down to what you want to learn, what you are able to learn and where your value of time / money. Basically shops like us turn money into time. Sometimes it makes sense for people to spend their hours at their job, then pay a shop to get the panel done. When you get it you know it's been tested, and if you have a lot of money into avionics you won't have to worry about the smoke test.
Anyway, I don't intend to extole the virtues of having it done professionally as your only choice or try to stump for business. Obviously it's been proven by the majority of homebuilders that it has and can be done by the builder. Like shooting your first rivet, it's something you can do if you're carefull, patient, willing to learn (along with willing to make mistakes) and have the time. If you don't have the skill or time, then go work at what you do well and pay someone else to do what they do well as a professional avionics shop. If not, do it yourself!
The last option is somewhere in between (what we end up doing for more builders than just doing complete panels) is to have the basic avionics wired up by a shop and then do the rest of the panel yourself. You have to buy the avionics anyway, so having the shop make sure everything is appropriately wired together isn't much more. Read some articles, get the Bob Nuckolls book and maybe even have someone help you. I think you'll find the better known avionics shops who are experienced with RV's will be flexible within your needs and help you with what you can. Sometimes that is doing the whole panel, and other times it's just helping you do it yourself.
In the end, it comes down to each persons situation. I spent time sheet-rocking my basement years ago because I wanted to do it myself and save the money....it came out ok, but Lord I learned a lesson.....now I'll just do what I'm good at and pay those who are good at what they do to come and do it for me. That sort of is how us avionics shops survive!
Cheers,
Stein