Getting ancient applications off old SPARC hardware is trivial - just use Charon-SSP.
I've benchmarked this and on a modern processor (AWS C5 instance) you get core performance equivalent to a 1.5 GHz UltraSparc III (I got some old SPARC boxes from ebay for the purpose of doing this comparison, also because I was nostalgic for the old days).
Charon-SSP is not as fast as a SPARC64, M5/T5, etc. but those ancient applications aren't running SPARC64/M5/T5 (which can't boot Solaris <11 anyway) - and any application running on a SPARC64, M5/T5 etc. can run on the latest Oracle hardware.
Migration is generally done using ufsdump/ufsrestore (you'd need to install a fresh Solaris OS on the Charon-SSP emulated hardware first.. so finding an old Solaris 8 ISO is going to be hard, but not impossible.. I found a Solaris 2.5.1 install disk on an abandonware site).
Re: ebay, I managed to get a v210 and a T4-1 for fairly cheap recently. The 32-bit SPARC's (SS5, SS10, SS20) are hideously expensive, although an Ultra 5 can be had for $200 and with the NVRAM fixed. Too bad, I'd have liked an SS10 or SS20, I learned Unix on Solaris 2.3 on an SS10.
Compared to DEC, IBM, or SGI hardware, Sun hardware is actually the cheapest you can get on ebay. I'd get an M4000 but the shipping costs would kill.