I think the break even point for the upgrade is actually $3k/year, not $2k/year?

The standard Gold Star Membership costs $60/year, and the Gold Star Executive Membership costs $120/year [0]. This is an additional $60/year (ignoring sales tax, etc.).

In order to break even, you need to earn at least $60 using the 2% cash back from the Executive Membership in order to cover the upgrade. This works out to ($60/year) / 0.02 = $3k/year.

[0] https://customerservice.costco.com/app/answers/detail/a_id/8...