Why have the prices of Marantz and Sansui speakers have gone up so much? Whyyyy???

Some of the receivers etc  from the 1970s are collectible now people are buying the speakers and TT etc to get complete systems. This in no way obsoletes any audiophiles gear selection so just relax. It doesn't mean that they are inferior to you they are just collecting as humanity has done for ages.

I understand, but if im putting a vintage system together you can be sure the speakers will be worthy of listening to and enjoying.

I dont see realistic speakers going up crazily in value like marantz and sansui but willing to bet the realistic sound alot better

There is one speaker from that era which have always had a following the Realistic (Radio Shack) Mach 1.  I only know people have sought them from the start and haven't hard any myself.  They are still popular but have gotten panned by people used to current audiophile standards, i.e. expecting sound quality equal to or better then todays offerings. I have some old Marantz book shelf from a garage sale I have never used,  perhaps I should put them on auction.