This "felt" content light but they're definitely teasing something by Fiona's reaction to bringing up the teleport stones. maybe Fiona was in the dungeon for punishment? Poor and needs the money?
She has cigars, so I somehow doubt she was sent as a punishment. She's definitely poor and in desperate need of money from her reactions with the crystals and must have chosen this unpopular high difficulty dungeon in the hopes of somehow making good money.
That reaction on page 4
This dungeon has no known working teleporter, i guess? That looks like the case from her reaction
My first thought was that you need to be "registered" at a teleporter in order to use it as a destination. Since Saeki has been transported from another world, she's never touched any other teleporter from this dungeon and thus wouldn't be able to use it to escape the dungeon without clearing all of the floors from the bottom.
But who knows, maybe Saeki can't use a teleporter to escape the dungeon, but maybe to get back to her world?
With that said, what will they do about the home center and the pets there as they move away from the bottom floor and if Saeki actually manages to escape the dungeon? I also wonder about whether monsters might respawn after some time (and if they do, would they remember their previous existence in the dungeon? The dragon might not be as easy to beat then).