We were starting to think no one would ever ask. Scale-ability is one of the biggest features that sets BePro listings apart from other directory options. Since you are a developer, I will focus on technical aspects
You are right, wordpress does not scale well if everything is stored in its tables. We see all of the competition using meta values to store content which is 3 joins per value. We store *NOTHING* in meta thats searchable. *EACH* of our addons and the base plugin itself, creates a new table if its storing searchable information. That way, info cost N per set where N is the number of joins (elements). That's instead of N * X where X is the number of elements. Our database calls were designed to be as efficient as possible.
For the listings, there is no wordpress loop. That process is intensive, pulling content that has absolutely nothing to do with our operations. Each of our listings are generated by templates. We launch each template iteration in a "for" loop. Checkout bepro_listings_frontend.php. The entire file is either functions called by templates, or functions that start the template process.
We also do our own database calls to retrieve all records. Please check our database function in the "bepro_get_listings" in bepro_listings_functions line 394. Look at how we retrieve information. You will notice how other functions are allowed to hook into the database request. This means, all of our addons communicate and share information instead of being standalone and initializing multiple database requests. We have not seen this anywhere else, it was engineered by us, and by itself sets us apart from any other competing solution. So our addons scale operations at the rate "N"
You are 100% correct, when it comes to scaleability, there is no competition for BePro Listings. Look closely at all the major directory solutions on wordpress.org as well as off, and you will notice them slowly changing to imitate our architecture. Thing is, most have to rebuild from scratch to imitate what we have done. We are still waiting for, someone, anyone, to prove us wrong
Since everything works on templates, BePro Listings can be implemented into any theme. In fact, we constantly have users bringing us their favorite directory design that they bought, and asking us to replace *ALL* directory features with BePro Listings. This is a no brainier, because you cant see the internals of themes until you buy them, while BePro Listings is wide open, allowing testing before you buy a thing. Users quickly find that popular themes usually (not always), have extremely bad code under the skin, preventing customization and expansion.
Oh, and in terms of amount of listings, we see lots of claims of 100,000+ from the competition. So we wont waste time with silly numbers like that. Obviously with the right server, you can power nonsense.
Come on over to our website forums and we can discuss more. We work closely with developers adopting our product. We actually provide development hours and work with you when requested.