If you can buy a $2000 server to run solaris, why spend a Million dollars for a sun system?
Sun isn't expecting them to, they expect them to buy Sun's Opteron servers to run it. And, BTW, they cost more than $2,000 and a lot less than $1M.
Xeon servers will not run Solaris x86 64 and even HP's Opteron servers are neither cheaper nor better.
Petz