You'd also be in competition with St. Jerome's Classical program and the affordable Montessori program (that moved from Mt. Rainier to DC), both about $7,000. Montessori has the additional benefit of allowing kids to transfer into the county Montessori after age 4 for public. If you don't have a strong middle school program forget it. A lot of parents willing to pay for private school are really paying from K-5 for a guaranteed spot in middle school since that is the biggest problem area in the county.
You'd easily get parents willing to pay $14,000 for a high quality middle school since by that time private K-8's are filled and unless you get a spot in TAG, College Park Academy, or the creative and performing arts program you're out of luck. Parents in this area don't always have the finances for private K-12 all the way, but there are many that figure they might have to pay private for middle school.
Something like DC's charter school BASIS would be in incredible demand here.