How cheap can you go and still be happy with the sound?

I’ve owned three tube amps (I still own my first one) and the best sounding I ever owned were a pair of monoblocks that could be a bit unreliable so I replaced them, but they were the amps with the highest MSRP.

I own three preamps, and each successive preamp cost more than the last one and each one had sonic characteristics that were distinctly better than the one it replaced.

YMMV, but my experience has been that every increase in sonic performance that I have ever experienced has required an increase in expenditure. To me, that does not seem all that unreasonable.

Bose wave radio while washing my car in my garage. Better than nothing or accidentally getting an expensive piece of equipment wet. Happier than nothing. Kind of a trolling conversation though.

For me:

A balmy, early summer’s eve,

My favorite chair on the back deck,

A Sony Walkman CD player (used) - about $20,

A pair of 30 yr. old Bose headphones - $100 (back in 1990),

A six-pack of beer - about $8 including tax

I had a pair of Sony sscs5 speakers for the deck (bought for ~80 dollars on a amazon sale). It was... meh ok. I put the GR research upgrade kit in it, ~300 dollars and it has become a creator of happiness.

Can't do the liquor anymore... but, the Sony does work well with the coffee/cigars on my deck. 

A six-pack of beer - about $8 including tax

I don't that exists in my town. Maybe for $11

I found that the dirtier and nastier the task, the more forgiving I am of flaws in audio quality.  Listening to music while cleaning the bugs off the motorhome, for example, does not require a pristine delivery of an audio masterpiece to be a beneficial musical contribution..  Just something more pleasant than standing on a ladder while removing bug guts gets a "pass."  Working on a classic car?  Same rules apply, but  genre also matters.  The laid back sound of California surfer music instrumentals lowers the stress level and reduces the "tool throwing factor" by 50%.