I'm in the process of reading Temple Grandin's book "Animals in Translation". So I've come upon this posting about deer-deflecting strategies just as I'm simultaneously exploring Grandin's observations, insights & advice on how to learn to see the world the way prey animals & grazing livestock species see & respond to the world. Although she writes & lectures more from the perspective of how to humanely and calmly manage livestock (&/or pets) that have a nervous system based on the survival priorities of prey animals, the principles she applies to moving prey-animals calming into and through various spaces, needed to corral & care for them, would seem to me to offer tips on how to deflect, spook & redirect an invasive grazer as well.
In "Animals in Translation" she emphasizes that we need to retrain our perspective/outlook to try seeing & observing the world of "threats & dangers" from the prey animal's perspective, which she explains is entirely sensory & heavily visual. With a narrower range of color vision, high contrast between light & dark, the illusion of bars or confusion of high contrast color-tones or shadows may do more to spook deer than barbed-wire or a thin wire that's run 6'-8'up (even if it is electrified). From reading Grandin, I'm suspecting that running a string of fluttery white and black flags might buy one as much deflection as anything... because of the spooking factor & triggering caution over approaching something that is changeable & hard to ID, hard for the animal to "read" or categorize as "safe".
It makes me wonder if stringing CDs in a manner that lets them spin & flutter might be effective. An experiment with putting inexpensive high-contrast whirlygigs on the fence posts might be interesting.
I think I would be tempted, by Grandin's observations, to go photograph my deer-proof fence from the deer's side, at deer eye level, and then set my camera to view in gray-scale in order to get a better sense of how the deterrents look to the deer. I suspect that thin gray wires may be nearly invisible while clipping high contrast fabric strips (or large stripe or block pattern) to the wire with clothespins might be visually "more spooky" to a grazer (& perhaps less costly than an electric top-wire). Though I also suspect, if you have a regular neighboring herd vs deer passing through, it may be necessary to switch things up periodically so the "spooky" stuff stays unfamiliar, new & uncomfortable to be around.
In this thought-experiment, in order to maintain the fence's ability to spook the deer, if you want to redirect them away from your garden crops, I'd be inclined to set up the alternate browsing goodies some distance away from the fence & possibly in or near some comforting "cover". Offering alternate grazing goodies near the fence, but on the deer's side, may stop the fence jumping in the short run but it may also desensitize them & make them comfortable with grazing near the fence. In the long run that may just serve to neutralize the fence in its role as a discomforting barrier to avoid.
Of course, Grandin describes all the rationale for this far better than I ever could. The thought I'm really offering here is that for those who are really struggling with a lot of deer pressure, & who are looking for humane & low-cost solutions, reading-up on some of Grandin's work might give you some further ideas to test before you you have to go all-in with more electric runs or other more costly materials. Although I have not yet read it, Grandin also has a book on Livestock Handling for Small Farms that looks to me like it could be a worthwhile read for homesteaders. This is a different book than the one written for livestock yards/larger-facilities (where she started her career).
If you'd like to explore her work, without buying one of the books, she has a pretty extensive & pragmatically oriented website loaded with free info & advice covering many species from pigs to antelope. Her books include entertaining stories & contextual tales in the set-up to the science, but her very unglamorized website just cuts right to the facts & straight talk advice on what works with what animals (& cites research as well)> https://www.grandin.com/
If you're not a reader, but are curious to learn more about her observations on how animals think & how we can interact with them more effectively (both more kindly & more cost-effectively) you can find many YouTube videos of her giving farm talks in that vein such as this one which is titled as being about horses but which ranges around to dogs and other barnyard species as well https://www.youtube.com/watch?v=_vTNdbDb2Vg
Bottom line for me, in reading her book as I was reading this post... I was just struck by how we are here trying to construct our human idea of what might be the most effective warrior deer obstacle course. Many good ideas, but most may still be grounded in our own perspective: our human view of the problem, our omnivorous primate cultivator's view of our garden & what we conceive of as a "barrier" or detraction to entry.
If I weren't in the middle of reading "Animals in Translation" this week, I know I would've consumed this posting's conversation in a mindset of seeking to learn: How high should I make it? when triggering a grazer's fear of being preyed upon while eating may well be a much bigger detractor for this visually hypersensitive skitterish (high jumping) muncher than building a higher fence or adding an essentially invisible hot wire. Grandin's book doesn't specifically present a solution for deterring invasive deer but reading it has given me a new perspective on how to approach the problem. It also reinforces the comments here that suggest: While we busily test the rest, the fact remains ~ Dogs are Best! ...with cats that think they are mountain lions being in the running, it seems, as well ; >