just saw this at ebgames website :

https://ebgames.com.au/3ds-210104-Shovel-Knight-Nintendo-3DS

as i am looking forward to get this game, what is the "extra" we got in pysical retail release? the price difference is quite big 

Oh cool, if it comes out in Australia likely will come out elsewhere too.

• Specter Knight’s Campaign: A full campaign starring the shadowy scythe spinner!
• King Knight’s Campaign: A crazy campaign with the gilded goob himself!
• Battle Mode: Duel with up to 4 players as your favorite heroic or villainous knight! (Wii U/PS4/XB1/PC exclusive)
• Body Swap Mode: Did you ever wish Shovel Knight was a lady, or Shield Knight was a dude? Well, now you’ll be able to change them all around, along with the rest of the cast!
• Oh, and one more thing: Every boxed copy of Shovel Knight will include a lavish instruction booklet similar to the Kickstarter reward. No 2-page inserts here! You deserve a full manual, to hold in your hot little shaking hands and pore over as you wait to get home!

Also probably a placeholder price.

so those modes does not available in eshop version?

I've been thinking about buying the XBONE version. I like that indies are getting physical

Nice - I have already preorder it from Game and the Amiibo too but this is separate and not included in the price of the game!