I suggest posting the spell scroll prices (i.e. how much does scribing the spell cost you) as an ICly useable knowledge. The reason behind this is to prevent unpleasant surprises upon scribing the scroll. After all, wizards know what all they need to scribe/cast the particular spell and can estimate the price by checking the marketplace or other reagent suppliers. It should also prevent awkward situation in trading spell scrolls and generally give an incentive to the nascent spell scroll market.
One might argue that by posting this, the world will lose some of its mystery and prevent any more shady competition methods from being applied. If such are the concerns, I suggest scripting a possibility to have a crafting submenu (which would be accessible only if the PC has the Scribe Scroll feat) where all the spells the PC knows are listed and upon clicking on them, the player sees the price. Thus, the wizard would know how much does scribing the spell cost only if he/she knows the spell.
Or, making it in the same way as the ability and skill rolls are being done, i. e. "/o *scroll Shield*".
That would also allow modifying the price from time to time to reflect the changes in trade flows, and make the wizard aware of the modifications, which he/she would well be. E. g. the massive bat attack on Sanctuary that happened not so long ago would have decreased the price of scribing a scroll of Fireball for some time. ;)
Is such a thing doable?