On a multi site set up, each sub site has their own MarketPress store.
Some of the stores will sell some same products (for instace, identified by same SKU number), which will have same prices.
The super (network) admin can adjust the prices of these (same) products that published on different sub sites, once he changes the price of a certain product, each subsite will sync to this new price for this product instantly.
For instance, each subsite admin/owner is a member of a footer team, and each of them can sell tickets online for an upcoming event and make some profit to their own wallet. Very importantly, the ticket price is fixed, and nobody can sell it higher or cheaper than the standard price. So someone got to be able to set and change the price universally once needed, otherwise, it is not practical to change the price on each sub site individually.
How to do this with MarketPress? I know custom coding may be needed here. Just want someone who knows WPMU and MarketPress better to point us to the right direction.