It depends largely on where your current pricing is at. If you already have a majority of names priced around $2,500 or less, cutting your prices in half will have almost zero impact on the number of sales. You'll just make half as much money for what would have sold anyway.
I can 100% guarantee you it won't double your sales. Even if it did, that wouldn't be your break-even point because you'd need to replace twice as much inventory. Actually, if you're pricing most of your names around $1,500 you should raise your prices 50% not slash them, and use the extra money to scale up your portfolio to achieve more sales.
For consistently selling 20+ domains per month retail, I would rank the factors in this order:
1. Quantity
2. Pricing
3. Outbound
4. Quality
5. Luck
STR is like a bell curve when compared to quality, it's not linear. Garbage names will have a very low STR, but so will very high quality names. The STR on LLL․coms is around 0.3% which is pretty abysmal, at my old job the company owned about 10% of them. But when one hits you might be making six figures profit, possibly even seven.
If you already have average quality names that are reasonably priced, improving quality even more is not your path to doubling your number of sales, you'd either need to double the size of your portfolio or do outbound sales as a full-time job. Quality is your path to doubling your average selling price though, which is an equally good goal to have, maybe even better given VeriSign price increases.
To hit 20 retail sales per month you need a large portfolio of names priced in the sweet spot if you want to do it passively, or with a smaller portfolio you'd need aggressive outbound sales. For passive we're talking 15,000+ average names, or 30,000+ decent names, or 60,000+ crap names. That last one wouldn't cover renewals though.
I think more people in this industry need to get comfortable with outbound sales and putting in long hours. Buy a handful of names after researching who you could outbound them to, and don't buy any more until you've reached out to everyone multiple times. Rinse and repeat until you find what sells, and then start scaling.
Too many rely on #5 above. They don't have the quantity or quality to see a sale within a few years, and are too lazy to outbound, so even with fair pricing they're missing too many factors and don't have a shot.