Not really. The lower tiers are only less efficient on platforms that require purchase through an app store or other payment processor that takes a large cut. Buying through a gift card or through the Roblox website or non-Microsoft Store PC app gives more Robux for the same price <https://www.roblox.com/upgrades/robux>. These increased rates are also balanced to prevent the lower tiers from being less efficient: the package for 800 goes to 1000, whereas 10 000 goes to 11 000.