It is a 30% commission on the order value for the 'premium plan', so yes the restaurant absorbs the cost. Interestingly they also have marketing services in platform, so some businesses might effectively be paying greater than the 30%.
In addition to that charge, consumers also now pay about $5 delivery fee and a 'service fee' of 10% up to $4. It is quite an expensive way to eat lukewarm food.
I have not seen many businesses have two tiered pricing for delivery and non delivery. You are allowed to, but I've read it is encouraged to keep them the same, this will prevent customers being turned off if they know its a lot cheaper in store. Its not great though, essentially walk ins are subsidising the uber eats orders.
Yes, independent shops would have lower turnover as they don't have the benefit of a brand. However, selling a large for $15 would make up for simply just doing more turnover at low margin. The $5 pizza is trying to compete with cheap Maccas lunch deals etc. It would be destructive to franchisee margins though.
The cost to set up these stores is hundreds of thousands and DMP forces francihsees to buy everything through them, safe to say they get bent over a barrel. The franchise sector is a pretty scummy business as evidenced by Retail Food Group scandal.
I have a lot of sympathy for people tied up in it, some make decent money, but most would be better off working for a salary.