I would have to agree that those buttons are too far gone for any cleaning, but not so bad that they can’t still be used.
There is a whole thread (actually a bunch of threads) about elektron button deterioration, lots of moaning and groaning going on over there if you want to check it out.
Now to be fair, the issue sucks so a lot of the moaning is justified, especially since it’s been quite common on the older ones.
The last time I checked it was about $2 per button cap if you’re out of warranty plus something like $12 or $13 shipping to purchase through elektron support, and with a blue box, you (like me) are out of warranty.
Something like 38 buttons on the machine, and even if you only replaced the trigs (just the caps for the trigs) that’s still something like $32 plus shipping and probably tax if you live somewhere with sales tax.
I know it sucks, but the digitakt 1 market is terrible right now as it is, you’ll probably lose money on investing further in the DT1 at this point and whatever you intended to spend on the buttons, take that off your sale price and just make a clear disclaimer that the buttons are displaying wear and the digitakt is sold as pictured.
You’re more likely to get someone who will compromise on the appearance of the buttons for a lower price because people with low budgets are often willing to overlook superficial stuff, especially when you can see the rest of it looks nice, has a box, original power supply etc. Lower price is the only way you can differentiate from others right now anyways, the market has been flooded since dtII released.