Subtropical latitudes in continental US markets, you're looking at like $2/yr/sq ft of value for the power output.

I'd want solar panels for like $5/sq ft installed, expecting 10 years of life.

It's going to cost $1000 minimum to install, so the panels need to cost $2/sq ft x 300 sq ft to make this worth it. $1000 to install 300 sq ft + inverter and electrical panel upgrades seems light but might be reasonable we'll go with it.

Larger than a balcony, but maybe in the realm of possibility for a roof.

Right now solar panels cost what? $10 per square foot? Have they reached the physical limit of economic production/storage/transportation at $10 per sq ft or can it go lower?

(Let's not get into battery micro-storage economics).