my kids were homeschooled until 8th-9th grade. DD started team at age 7 (pre-team at 5) - training 12 hours a week - was up to 20 hours (level 7) by age 10. Did well with her schoolwork, did ballet 2 years, played violin in local youth orchestra, rode horses, etc....homeschooling really helped with the scheduling (we homeschooled for non-gym reasons). The boys switched from rec to team on a whim at ages 10 and 6 - and were training 16 hours a week a couple of years later, my older did one year of 20 hours but gym/music and high school were too much for him.
DD quit gym in 8th grade (and started brick and mortar school) after a year of on and off with new gym/puberty and fears...now trying to come back as a high school freshman with a very heavy academic load of AP and advanced coursework...its been really challenging for her to do even 12 hours a week and keep up...but her schedule was not planned with gym in mind. If she sticks with it she'll need to go 20 hours next year (L8/9) and will have to adjust her school schedule (she's already got 2 full years of credits and hasn't finished her freshman year, so she can do so).
We don't take big vacations - other than once every 4-5 years - between three kids/activities/work and finances, its just not in the cards. We do make some adjustments to meets and practice schedules due to finances - although there were only a few years with all three doing high hours.
Its all in your personal (as a parent) priorities - if you are fine with family time being taking an extra day to go to museums in whatever city the big travel meet is in, and can adjust to late night dinners, lots of driving etc. that works - and would be the case with any serious middle school/high school sport/activity - my older kiddos music stuff is way more expensive and time consuming for me than gym. But our house needs a lot of updating that will not be getting done until they are in college, we are frugal in many areas, and I have taken the controversial approach of telling the kids I will support their activities and academics to GET INTO college/conservatory, etc but I'm not saving money to pay for THEIR college education (it worked well for me through medical school, loans and all...I know many would disagree with me...).
In the end, I personally don't know tons of kids who got to high levels and had their parents pull the plug due to finances - most of the families that I have known who did that get to that decision while the kiddo is in elementary school and complusories...and after all, its how you frame it - kids will be disappointed, but in life its better to be happy for the years you did get than sad about those you didn't and as parents we disappoint our children regularly!
I really do think that there are so many variables, I don't think you have to decide if you could support a L10 now - but you should decide if you like the idea of supporting your DD as a compulsory and all that entails. There are huge pluses to a high school kid having an intense activity, and huge disadvantages, financial and otherwise. But its much more likely that your kid will guide you in that decision - and not all L9-10s do camps, college recruiters, private lessons, outside PT and strength training, etc...in fact, I personally think it is sort of "self-selecting" in that the families that are ready to do so will produce that kind of a high level gymnast...
what's more, having had a son who is quitting at L10 but did manage to do a sport through 2 years of high school and a DD who after taking what will be 3 years off competing , even if she doesn't run into issues again really can only hope for at best one year at L10 and no chance to do gym after high school (so no need to push with "extra financial stuff" and can be a laid back gym as long as she's happy and safe), and my youngest who just learns skills at his own pace...I'd say - if gym is fun and healthy for your daughter and you can afford competition at the next couple levels, I wouldn't worry beyond that...but don't promise the Olympics!