This question came from someone a few days ago and had to think about the time, costs and efforts to do this modification and this is what I replied with:

Thanks! I should have probably said that this modification requires an “intermediate” level of soldering skills, not to mention a lot of patience.

You know, I wouldn’t want to do this mod on an existing pair of 770s because sometimes people abuse their headphones and the drivers can be damaged, so I would rather do this on a new pair of 770s. Currently these cost about $200 new. I’m a big believer of burning headphones in, each model can benefit from some “breaking in” with listening to music, and I constantly hear these particular cans sound best after at least 100 hours of breaking them in. This means I would first burn these in for 8 hours a day for about 2 weeks (I remember burning in my Sennheiser HD650s for about 200 hours and had different hip hop CDs played on them for about a month, some people like to use pink noise, but I prefer playing music through them).

After the two week burning-in period, I would then start working on the modification. I took my time with mine and it took me a few months to complete it, but if I were to work on this again, dedicating an hour or so every day, I could have it done in about a month (I’m mostly occupied with audio projects and would have to find time to do this without rushing). I would estimate that just doing the modification would take me a month, probably a little longer if I’m really busy with audio engineering projects.
This doesn’t include painting, I had a great time breaking out the airbrush and mixing paint again (I used Enamels), so I wouldn’t mind doing this but this takes a good amount of time as well. I lightly sanded all the plastic pieces (so the primer and paint would bond better) then I gave them a coat of primer, let the primer cure for about 5 days and then painted; I used two coats with another 5 days in between, and then sealed the pieces with Tamiya lacquer and remember giving it about 2-3 coats of that to protect the paint job. I can work on the rest of the modification while working on painting the parts, but still, this would add a couple of weeks to the whole project, so based on how much work this would take, and the amount of time, this is how much, how long it would take:

Modified DT 770 Pro 80 – Includes brand new headphone, modification, detachable cable, flight case: $700 (2 months wait time)

Modified DT 770 Pro 80 Painted – Includes above plus custom paint job to whatever color you want: $850 (2 ½ months wait time).

Because this is a custom project, payment would need to be sent up front, so I could then buy the headphone and all the necessary supplies and parts. Thanks for asking!