Install CPA is the wrong north star
Apple Search Ads optimizes toward taps and installs. Subscription apps make money when trials convert and retain. A $2 install with 0% trial rate is infinitely worse than a $8 install with 5% conversion to a $12/month plan.
LTV-based bidding means setting max CPT/CPA from what a customer is worth—not what competitors bid or what Apple suggests.
The profit cap formula
Max CPA = LTV × conversion rate × margin
LTV — subscription price × expected retention months (or observed RevenueCat LTV). Conversion — install-to-paid rate. Margin — profit after App Store fees, refunds, and COGS you choose to model.
Try your numbers in the ASA bid calculator.
Cold start vs observed data
New apps lack conversion history. Reasonable defaults: ~2% trial-to-paid, ~3-month retention, ~50% margin—then tighten as RevenueCat data arrives.
Subvra uses cold-start assumptions until your account has enough installs and revenue, then shifts to observed conversion and app-store or RevenueCat pricing for LTV.
Brand vs non-brand caps
Brand keywords convert at higher rates; you can afford slightly higher CPTs but still within profit logic. Many teams use ~20% of the generic max CPA for brand as a safety ceiling—never bid for impression share at any cost.
When to raise bids (and when not to)
- Raise only if keyword ROAS is positive for 7+ days and impression share is low
- Never raise because CPA ‘looks good’ without revenue attribution
- Lower bids when spend exceeds 2× max CPA with no attributed trials
- Recompute cap when you change pricing or intro offers
Bottom line
LTV-based bidding turns Apple Search Ads from gambling into arithmetic. Structure campaigns by intent, cap every keyword, measure revenue in RevenueCat, and automate only what respects the cap.