I'm sure this probably has been requested before but is there an option to get card values from Star City? One could pick between TCG player or star city, or maybe even other sources.

even better, a 2nd level implementation to pull the average (mid) or general average price from the multiple sources that get implemented?

I'd be very surprised if SCG makes their pricing data available through any kind of API. For a wide variety of reasons, it's a really bad idea to try to scrape HTML for values like that.

I'm not sure how ark42 gets their price data but they only show SCG.

Deckbox gets a referral when people click the price and order from TCG. Not sure if Star City has a referral program, but I doubt it. That would be one reason not to show other stores...