How much are you willing to wager that filtering out moving dots with intensity comparable to or somewhat below the statistical noise in an instrument is easy?
Furthermore, for transit-hunting experiments, a slight dip in a star's brightness once per year or once per decade is the entire signal. Even if the satellite doesn't produce a moving dot, surely it cannot be transparent and non-refractive.
Lowered launch costs can't compare with the expedience of ground-based experiments.
Some things work really well in space, some do not. Low-cost launch will revolutionize some experiments, but not all.
Building radio experiments like SKA, big telescopes like TMT, or starting up innovative low-budget instruments like Dragonfly is still impossible with low-cost launch. In the latter case, until a graduate student with a screwdriver can make daily adjustments to an on-orbit instrument, we will lose the earliest-stage R&D capability.
Finally, it is essential for our future generations to see a dark and unfettered sky with the human eyeball. That perpetual perspective, for 7,500,000,000 people, is inaccessible with launch vehicles.
Furthermore, for transit-hunting experiments, a slight dip in a star's brightness once per year or once per decade is the entire signal. Even if the satellite doesn't produce a moving dot, surely it cannot be transparent and non-refractive.