The article states the money reflects the amount needed for her care. Daily Mail is known to amend articles as they go so this may not have been shown earlier.
I've worked with Down Syndrome adults, quite elderly about 55 plus age range. Their parents have passed away and most need a lot of care which is provided by the state in the UK. Downs syndrome children from my experience are bright lovely people, adored by all around them with dedicated loving parents. If a parent is willing to take on the joy and challenge of looking after them then that's fantastic. However the challenges continue into adulthood, I personally would chose not to continue with the pregnancy. Surely better this route than an unwanted child.
The couple is American, may be lacking in health care insurance, and having no NHS safety net this may be their only option. Until I am in that situation I can only assume how I would react, I may find myself there one day and decide to proceed with the pregnancy and deal with the challenges. Until you're there, you never know.
I doubt it's about perfection as such, more an unwanted situation which the couple believed they had planned against and now find themselves with a disabled daughter and no financial means to support her required healthcare.