Unless you created the asset, then I don’t think you can really get it into your group.
Same applies for gamepasses in group games.
The most common way is to have 2 tabs open, one being the purchase screen and the other being the config page. If you change the price to 1 robux, purchase it, then change the price back, you get it as cheap as you can. You just want to be quick about it, so no one else gets it for 1 robux