It’s not valuable. It’s landfill stuffed in their garage that is declining in value and re-usability the longer it sits there. If it has value, they would be willing to list items individually and sell them. If it was precious, they would be taking it with them when they go.
Maybe they spent $200 on something that could sell for $125 second-hand. Getting the $125 is the hard work of listing the item for sale, replying to a couple of texts and meeting the buyer. This is how you ‘earn’ $125, otherwise, you have nothing but a hunk of sunk cost in a piece of landfill. The ‘value’ to the seller is in the work it takes to sell, not the unneeded item sitting there, becoming a home to vermin. If the garage is packed to the gills and they are more interested in having it empty than in getting 50% return of the purchase price of all that stuff, they can hire a person to staff a garage sale, throw open the doors and take any offer on anything. Let the $75 bike go for $5, for example.