You would probably make up for the cost savings by building something strong enough to withstand the forces of achieving Earth escape velocity in a fully deployed configuration, not to mention all the increased mass that would be required.
Since it's impossible to do maintenance on this observatory while it's in solar orbit, and since launches have strong vibrations and forces, it's important that the delicate and sensitive equipment be stowed in a way to minimize the effects of launch forces and minimizate the requirements for after-launch maintenance.
Since it's impossible to do maintenance on this observatory while it's in solar orbit, and since launches have strong vibrations and forces, it's important that the delicate and sensitive equipment be stowed in a way to minimize the effects of launch forces and minimizate the requirements for after-launch maintenance.