Some bundles are available in tiers.
In such bundles, each higher tier includes all the games from all lower tier(s) and some more for a slightly higher price.
- Tier 1 = Game 1 and Game 2
- Tier 2 = Tier 1 (Game 1 and Game 2) plus Game 3 and Game 4
- Tier 3 = Tier 1 (Game 1 and Game 2) plus Tier 2 (Game 3 and Game 4) plus Game 5 and Game 6
Typically, higher tiers are better value as you get an increased number of games for a smaller increase in price.
Having purchased a lower tier it isn't then possible to upgrade to a higher tier without purchasing the lower tier again.