It's crazy how fast the prices are dropping. I feel like they dropped by 40% in the last 6 months. The cheapest 2.5" drive available on newegg is now a flash drive. It's probably hard to make a spindle drive any cheaper than $50 for laptops. I have a feeling the prices are going to similar to usb thumb drives soon.
It's under $1 per GB on SSDs now, which is definitely affordable for average consumers (around $90 for 128GB).
I bought a 256GB SSD in Feb this year for around $360. That exact same drive is now $260.
The beauty is that SSD/Flash pricing is directly affected by Moore's law... so as has happened with RAM, prices halve / capacity doubles roughly every 18 months.
AFAICT hard drives seem to increase capacity fairly linearly, so we might very well have a cross-over within a decade.