I am using Marketpress in Multisite configuration with global cart. I found one little bug (i think). When i add a new product and set the price to for example 3 and hit publish. It saves to price okay in the post_meta table. But it doesn't save it in the wp_mp_products table. Only when i hit the update button again for that product it updates the price there. My guess is that the price which goes in wp_mp_products table is 'Sale price' which at the time of publishing is 0, but when the page reloads, its prepopulated by the 'price' field value. So now when the product is updated, it takes that value.