Any shop or website in the UK (not sure about elsewhere) has to have sold a product at a higher price for X amount of days before they can put it on sale and promote it as a sale e.g. 50% off.
I could realistically raise the price to $120 for 1 day and then put to $60 the day after and promote as 50% off, but it was only available for 24 hours at the full price, it was never that normal selling price.
2 days later I change price to $200 and a day later change to $100 and again put as a sale at 50% off, but the price has risen $40 in 4 days.
Foul play like this misleads buyers, trying to think they are getting a bargain when in fact they are being mislead and lied to, to try and convince buyers they are getting something cheaper. When you allow sellers to set their own prices then you need to have some fules which stop them abusing the price controls.
In regards to ADP, it’s better for authors, it’s not for sellers, buyers now have a much varied choice for their budget, e.g. I only want to spend $40 on a theme I now have some choice.
Sellers now have to fight with each other for the sale, and for some buyers, price is the main factor but I work with tons of buyers (they buy themes under their accounts, not mine) they are more interested in the design and features of the theme and not the price, one buyer chose an $80 over a $60 as it was better for their needs. Sellers need to make themselves stand out, promote your better support, promote your experience (20+ themes, 50,000 customers etc) and keep updating items so they fit the needs of the buyer.
In the short term, sales will be hit as buyers work out what ADP is and find out what separates a $19 theme and a $60 theme but it will soon settle as sellers will realise they are doing a lot of work for $19, their prices will soon creep up and you will find most will be in the $50-$100 price point, but at the moment it’s new so some authors are trying to get work out if selling at $19 is viable (it’s not when you have to support as well).
Over time the prices will rise imho, just need to give it time to settle and for the bottom feeders (as we call them) to work out being the cheapest doesn’t work, you just get the customers the higher priced sellers didn’t want…