A Bernina 830 record is definitely worth it. The replacement will likely last many years. I think they only have two of these type gears to go out. I inherited my mother's 830 and had the camstack gear replaced. At some point I will likely have the other gear go out but will probably try and do the replacement myself when that happens.
I have a 730 I got cheap at a yard sale and have replaced the camstack gear myself but as luck would have it, now the other gear is broken. It's having a time out cuz it pi$$ed me off.
I am going to be very careful in the future to avoid machines with plastic or nylon when possible...unless it's a fab deal on a Bernina. They are so worth it!