Why some preamps weigh 50+ lbs?

I only go for manageable products these days.  Lots of good choices.  Need not weigh a ton.  My 200 w/ch amp weighs 5 lbs and my Schitt preamp maybe just  a tad more.  My streamer is even lighter.  I still have 100 lb speakers and also more modular design ie monitors and powered sub.  Ability to set up gear properly in a room is perhaps the single most important thing to consider when choosing. 

Benchmark gear:   Thumbs up!👍 

Many use solid billet aluminum 

My magico q 7 = 740 lbs I have it on wheels and push it around for exercise. I think the krell 700 cx 150 lbs also on harbor freight expensive anti resonance dolly.the soulution preamp > 60 lbs.all used still going strong . My class d flea amps <5 lbs and makes my wounder why I have the other stuff.this is another funny post😁

Marketing.

Why do some preamps weigh as light as a feather? Cost cutting, poor parts/design and build quality results in severely compromised sound quality.