At my daughters gym the level 4 girls practice about 10 hours a week, the 5s 12 hours, the 6's 14 hours and the 7/8 girls are at the gym about 20 hours a week. We also have pre team at 6 hours a week and a Prep Opt team at 6 hours a week.
Prices vary between $170 a mo for prep opt and pre team and just under $300 a mo for 7/8 - plus meets ($60-70 each at 8 invitationals plus any sectionals/regionals/state that are qualified for) Leos at $70 every other year for new ones and warm ups $80, bags $10 and team shirts $15. And around here those prices are on the low end.
If your daughter continues to love gymnastics but the time and financial commitment becomes to much, check and see if your gym or one in your area has a Prep Optional team. It's new for our gym this year (my daughter is on regular team) so I'm not 100% on the full details, but the way it was explained when I asked was that it's team gymnastics for girls who don't have the time to commit to a full team experiance but want to compete.
Also don't be afraid to compare gyms and shop around if your gym isn't what you want or if things change to not suit your needs anymore. There are several gyms in my area (5 within 30 minutes - more than double that within an hour drive) with a competitive team and they are definately not all created equal. One is real hard core everyone will be elite hyper extended legs perfection is the only option most expensive gym in the area (their rec program is fabulous though!) - this gym routinely loses girls who burn out. One is real light, laid back easy going, these girls are not getting a real solid program and can't keep girls because of that (when you go to a meet you can see which gyms train well and which don't), another is going through some management and coaching difficulties and has been inconsistant the last few years so has lost most of their girls. The other two, one of which is our gym, fall inbetween the two extremes. The girls are getting solid programs, good training and progressing well - all while not being belittled, pressured, over extended and financially drained. But different strokes for different folks, so don't be afraid to try out different gyms. We evaluated all 5 when we moved and in turn were evaluated by all 5 before making our choice.