SSDs back then were approx 70c per gig, rapidly declining in price. It didn't have to be 500GB, that's a lot of space, a 150GB SSD could've worked in a starter pack. At ~100$, it's a good design move to ensure a big jump in data access speeds. Even another alternative: a 150GB SSD + 420GB 7200rpm drive would've been great.
My point is just that the PS's SSD is making noise, when it is such an easy upgrade nowadays and honestly barely needs to be mentioned as a feature. It's to be assumed nowadays that machines use SSDs or flash memory to propel software.
$100 when the internal hard drive probably costed Sony/MS something like $40.
There are some good benefits to an SSD, but even that modest sized drive would have put up the console's price at least $50. And people would only be able to install a couple games at a time.
Consumers would either pay a lot more or they'd be very limited in their collection. Either way, it's not ideal for a company to try selling to the average console buyer.