Hilda asks because of two reasons. One it's basic procedure to ask whatever deal you will get into. The more detail there is the more solid the decision. This is what she had been taught by house Antores.
The second reason was the fact that Egul seemed to be fixated on three months of working time. Normally when one counters a deal, the other party would compromise. But this is over-compensation. A mystic artifact is very hard to find or craft.
Holding onto one could boost the user's fighting power by 1 or more circles depending on how well it synergizes with your power. So giving Hilda one as a payment is too much, even for her work.
That means there has to be something going on in the tribe, something terrible enough to employ her help.
Egul crossed his arms and began talking.