Genuinely curious on what your value your time at here.
From this post you posted the spread of some ultra modern cards you dabble with, in particular SGC:
Card #1 has the highest margin at $15 raw to $45 graded gem mint / pristine.
SGC’s grading cost is $9/card, so your initial cost basis is $24. Ebay will take around 10% of the final sale price in fees, that’s another $4.50. Additionally I assume you’re shipping slabs for around $4/ea to end customers. In total you’re spending $32.50 to make $45, so you profit $12.50/card.
You mentioned you spend 2-4 hours per day on this and take a few weeks off each month as well. Have you broken down your hourly rate?