I've been working on a small personal project similar to this and agree that replicating the overall experience provided by Perplexity.ai, or even improving it for personal use, isn't that challenging. (The concerns of scale or cost are less significant in personal projects. Perplexity doesn't do too much planning or query expansion, nor does it dig super deep into the sources afaik)

I must say, though, that they are doing a commendable job integrating sources like YouTube and Reddit. These platforms benefit from special preprocessing and indeed add value.