Product analytics tools like Amplitude and Mixpanel get very expensive at scale. How do companies replace them?

Top 2 tactics: Existing Users and Industry Influencers. First, leverage the existing user base. Incent referrals with $5 for every new free user they get to sign up and start using PT Engine for a new domain. Second, reach influencers and offer them the same deal when they tweet / post to / email their audiences. Make the offer a 60 day free trial instead of the standard 30 day so that they are providing value to the people they refer as well. This is critical - don't make them feel sleazy, make them feel (and look) like heroes to the connections they share PT Engine with. That's $9k to get 1800 users, leaving you $1k for graphics, referral tracking system, administrative costs. I assume the $10k budget does not include your time - if it does you'll have to reduce the incentive, which will definitely make it less appealing. If you want to dive deep on reaching influencers, schedule a call with me at www.clarity.fm/ryandraving

Sure, it's correlative for technical reasons, iTunes / AppStore does not provide (yet, might change) a mechanism for that, so 3rd parties have to build their own. I recently discussed with people from Adjust and I was really impressed. HasOffers / MobileAppTracking seems to be a good choice as well.

NO, there no current tools available.

Much, if not all, of what you are looking for can be accomplished in Google Analytics using their Conversion Goals. I am not sure about *all* of it - specifically the information you want the merchants to have access to. There are tools that do analytics better and more detailed for applications like this, but GA is the best for your price point. You will want to plan for growth and moving to a more comprehensive solution, as your web app grows. Questions, comments, concerns, gripes, compliments or complaints? Book a call.

Google Analytics is the best free tool out there for this. Make sure that you are focusing your report on conversions - how many/what percentage of website visitors are taking action (filling out a form, buying a product, etc.). If you're interested in paying for help, you should check out Moz or HubSpot, but Google Analytics is your best free option for web reporting. They also provide some social reporting - which social networks are driving traffic to the site and which network referrals are leading to the most conversions. Good luck!