I'll say this. Perlite has no value in a soil with plenty of organics. It just 'helps'(wash your hard earned money away) drainage. In my opinion, most potting mixes are far too light. I use Ace Hardware's potting mix. It's about $3 per cubic foot and serves the purpose for starting and transplanting into larger containers. My experience tells me that the final planting should be in a mix that includes at least 10% heavy clay. The reasons. It helps retain water and nutrients. It helps increase soil contact with roots. In comparison situations I've had, the beds with clay produced plants 25%-100% larger.