At about 2 meters of aperture, you can quite well still do a single mirror at reasonable costs. If the launch costs like 60 million, the telescope would realistically have a budget of 60-120 million for the platform. On that scale, a series of 2m mirrors should be affordable - you would of course order more than one mirror, so you have a reasonable supply.

Considering that a single shuttle launch costet close to 1 billion and the Webb telescope costs many billions, spending 1 billion on a set of 5 telescopes including launch costs sounds like a worthwhile program. Which could be scaled to more telescopes as long there is budget.