No, no, no.
I currently work with an engine for searching flights.
Basically you got two major variations:
- Cached searches that searches flights in a database containing cached entries (fast, around 1-2 seconds or less per search depending on how large the cache is)
- Real-time searches via a GDS like Sabre, Amadeus, Worldspan etc (slow, 5-12 seconds per search)
You have to understand what underlying technology is used. If the flight comparison uses other sites (it's a meta search site) it will cache all entries and thus they use a cache mechanism. But you need to understand that such a site can have around 10 000 new cache entries per second so even if that meta engine searches in cached entries there's still somewhat of a huge overhead per search.
You also have to understand that a simple search can result in a couple of million possible alternatives. This is true for both the conventional real-time search made through a GDS but also for searches against a cached database.
In short: Yes, some add delay but the most delay you actually see is due to the amount of data that is actually being processed.