The math
Roblox keeps a 30% Marketplace Fee on game passes and developer products and you receive 70%, rounded down to a whole Robux: floor(400 × 7 ÷ 10) = 280.
Working backwards? See 400 Robux with tax. To receive 400 you would list at 572.
Nearby amounts
Both directions, using the same rounding as Roblox.
| Amount | List at this, you get | To get this, list at |
|---|---|---|
| 200 | 140 | 286 |
| 300 | 210 | 429 |
| 360 | 252 | 515 |
| 400 | 280 | 572 |
| 440 | 308 | 629 |
| 500 | 350 | 715 |
| 600 | 420 | 858 |
| 800 | 560 | 1,143 |
Robux transfer version
As a Robux transfer (10 to 500 per transfer) the recipient gets 360 and the game gets 40. Roblox does not document rounding for odd amounts, so this rounds down.