I always dye my hair at professional hair salon. It's not expensive here, about US$50. In my case, the dye never get washed out. But, as hair grows, I need to dye again every 6 months. Of course, hair dresser reminds me that I should shampoo my hair at least in 24 hour after dying.
Hairdyes products are very damaging to hairs and their roots. This is why I do not dye so frequently. One of my colleagues was diagnosed as alsopecia areata, and he dyed his hairs every month. I said to him that kind of frequnecy is a crazy thing.
Even I dye my hair every 6 months, my hair became strikingly thin and infirm. I can see the contrasting thickness difference between the old and regrown part of my hair.
A hairdresser said that there are some specialy hairdye products that dye each hair above 1 mm from the hair root to protecting the hair root and scalp.
If your hair indeed get washed out, then you may try coating or hair manicure products at hair salon. I also tried them, but I did not see any noticeable difference, and do not use any longer.
In my country, it is not so much expensive at hair salon. Dying + Hair manicure = about US $70 for my long hair that once reached my waist. Nowadays, as I have shorter hair, the expected cost is < $50.
About six months ago, I got my hair dyed, but I have no plan to do again in the near future. To protect my hairs.
Barbie~~