This is just how an economy is. You sell at equilibrium price where demand meets supply. With products that don't have much uniqueness between them, you have to sell at the price which the market dictates.
The economy in FFXIV is a free-market economy, meaning that it is solely dependent on us. Too many sellers for one thing lowers price. It's as simple as that. But as more people make losses, sellers will eventually remove themselves from the market. Supply of these items will fall. In turn, the items' prices will rise, promising profit to the few people that are left.
As such, it would be good to diversify what you sell to cover losses. Are you only selling boar hides? Well, sell some materia too while you're at it.
There will always be items that sell for less than what they're worth. Supply and demand will correct it naturally. People will both suffer and gain. That's just how it is. FFXIV's economy simulates real life.
