There is always DIY
4" x 8" SAMPLE 2D BLACK High Gloss Premium Carbon Fiber Vinyl Wrap Sticker Decal
Dealt with Vinyls wholesale/retail for 15 yrs.
we will just disagree
I'm a strong supporter of DIY, the Pre-cut vinyl stuff is of course going to be more costly, after all whoever is selling the pre-cut stuff is going to have to buy at least a somewhat cheap Plotter($1000) to reliably cut consistently sized wrap covers and I'm sure that goes in to the price more for some companies than others, all depends on how fast they want to pay off the plotter and how much they paid for it. Couldn't imagine someone supplying a large amount of pre-cut wraps without a plotter, so that has to be in the price.
Unless you're trying to wrap something exceptionally tricky IN MY OPINION using a pre-cut kit can actually be harder than just applying the wrap and very carefully cutting out the excess material, this way you can spend $0.99 on a 3"x5" sample of Vinyl and wrap your whole device with it. Most vinyl sites will provide samples of a 3x5" size or equivalent for around $0.99.
I prefer highly to use a flat sheet of vinyl and cut-out everything required while it is being installed, of course this is going to take a lot of practice to do correctly and cleanly but you can practice five times for a total of $5 if you go the route of buying samples. Hell, you could even buy a cheap/nice Olfa light duty cutting knife(what I use) and 3-4 pieces of vinyl samples for less than most of these pre-cut kits.
Both of these were wrapped with regular flat sample sheets and cut after the fact;
The Lethal box started out black, which I wrapped with 3M Atomic Teal, the Nemesis was brass and I chose the thick Hexis simulated leather vinyl because the extra thickness hid the tube seam which I wrapped over, making it look much more smooth and seamless.
Realistically pretty much any tube mod can be covered by a 3"x5" sample, there are also larger samples available for just a bit more if you have a larger box mod. 12x12 samples are $4.99, which is enough to wrap or practice wrapping pretty much any mod three times, if not more.
Samples
Source: I do full-car vinyl wrap on the side, my boss has a nice plotter and has taught me all kinds of awesome stuff.