The vitapods you can get before entering a tier you can get within two floors. This isn't a very good incentive to actually buy them.

Instead, you should sell vitapods people wouldn't find in that tier, like +15 vitapods from the tier 2 vitapod vendors and +25 vitapods from the tier 3 vitapod vendors. This would give players incentive to sink their crowns into those as insurance.