Let it be fixed at 10 legendary shards which is their initial cost. With the cores not being the endgame of armor masterworking anymore, it doesn't make any sense to have this restriction, not even the new ones at banshee have this ridiculous price increase. Also, banshee could start selling them as well, just for practicality, since he already sells the other 2.
For as much as it pains me to say, no. Spider is a gangster and the increasing price for something so sought after fits his personality. He's bad, but necessary.