It could be a sign of an unexpected alliance. Maybe Harry realizes that Snape has some hidden motives that are actually for the good, and the basilisk parts are a valuable resource that can help Snape in his own quests, like for potions or in dealing with certain dark magic threats.
Perhaps it's a form of apology or reparation. Harry might have discovered that he misjudged Snape all along. The basilisk parts are very powerful and rare, so giving them to Snape could be his way of making amends for all the times he doubted or antagonized him.
Perhaps Harry has a hunch that Snape is involved in some secret project or fight against the dark forces that requires basilisk parts. Harry, being the hero he is, decides to provide Snape with the parts to aid in this unspoken cause. It could also be a sign of Harry's growing maturity and his ability to see beyond their past differences.
They could also be used in some form of dark magic defense. Snape might use the basilisk parts to create spells or enchantments that can protect Hogwarts from dark creatures or dark wizards. Maybe he could create a magical barrier using the basilisk parts' power that repels any dark magic approaching the school.
He might be initially suspicious. Snape is a cautious man, and he may think that Harry has some ulterior motive, like setting him up. But after realizing Harry's sincerity, he could be grudgingly grateful.
I'm not sure specifically as I haven't read this exact fanfiction. But it might be about Harry Potter having some sort of interaction with the goblin nation and giving them the basilisk. It could involve political intrigue within the wizarding world as the goblins are often depicted as having their own interests and agendas, and the basilisk is a very powerful and dangerous creature.
In some fanfictions, Harry selling the Basilisk and Dragon might be a way to gain power or resources. It could also be a plot device to introduce new story elements, like dealing with magical black markets or secretive collectors.
In fanfiction, Harry having the eyes of a basilisk might be a creative way to explore his character in a new light. It could change how he interacts with others. For example, some might be repelled by his new appearance, while others might see it as a sign of his special status. It could also lead to new storylines, like him having to hide his eyes or learning to control the power that comes with having basilisk - like eyes.
It could signify a turning point in their relationship. They've had a rocky relationship in the original series, so this could be a moment of reconciliation. Snape might finally be seeing Harry as more than just James Potter's son.
The significance could be about character development. It might be a turning point for Harry and Draco to start seeing each other in a new light.
Maybe he needs money for some special purpose, like funding the DA activities more privately without relying on donations. He could also be thinking about using the money to research more about dark creatures in order to better protect Hogwarts in the future.
Perhaps in the fanfiction, the Basilisk has a hidden power that can only be unlocked by Harry's wand. A prophecy states that Harry must use his wand to unlock this power and use it for good. However, there are those who want to use the Basilisk's power for evil. Harry has to race against time to figure out how to use his wand to unlock the power and keep it out of the wrong hands. This would involve a lot of exploration of the Hogwarts secrets and battles against dark forces.