Finding a undamaged Summitar is a lot harder than finding an undamaged Canon 50/1.8. Very soft front glass, and if coated, the coating is extremely soft, trivial to accidentally "clean" the coating off the Summitar. The Canon has hard glass and hard coating.
That said, the Summitar is a lens with wonderful character.
Smaller but denser is the Canon 50/1.5, but quite unlikely to find for $300 these days.