I have a full head one time, then half next visit. My full head including cut with salon manager is £95, the half head inc cut is £80 so not that different.
I have my roots done every 10 weeks - sometimes 12 weeks and that is fine for me. I am a natural mouse too, so I do not have major routage. My hair is a bleach and a caramel shade, so the result is my hair is very very pale caramel/vanilla blonde but I love it, and love that my hair positively shimmers (especially on the lightest bits)
I would say go for it, you will look gorgeous and once you've started, you will want to continue to be that women.
My only advice? Do not do it yourself. Even if you go to the salon a few times do you know what shades you prefer and then try it yourself, that is better than just DIY first time. I personally would never DIY, but my highlights are very fine and I know my own attempt would be crap my comparison (plus DIY home kits do not contain as good quality bleaches/dyes, so you achieving your desired colour can be hit and miss)
There is a reason it is so expensive, because it takes the colourist bloody ages, so be prepared to be very bored, and get your appt as early as pos so you are not hungry and the hairdressers are at their most energetic. If you have appt at lunchtime you will be starving, and if you get one for late afternoon, the staff my be already in go slow mode)