Or even less if you pay income taxes to your state/country.
I'm good with any set of rules, they only change dev's strategy on how to compete on the market and answer to a simple question "is this market worth competing on?"
No matter how good your product is, you'll only get that many visitors/potential customers as they come to the store. If the price is capped to 5$, only thing that can make this market viable is the amount of people they will attract to the store. Let's say you're selling the ultimate plugin that is unbelievable for that price, and your product page is visited by 100 users per month. There's no way for you to make more than 100 sales, and you'll probably sell to a small percentage, let's approximate 1% or 1 sell a month. If there are 10000 unique (with a big percentage of new users) visitors per month, then 5$ is acceptable, as you'll earn around 300-350$ per plugin.
With 5-6 good plugins and low maintenance costs, you'll start to see some significant earnings. It seems like a good strategy, it'll force devs to create smaller, more defined plugins, with a focused and specific need, which are easier/cheaper to maintain. It'll also force devs to expand, offer documentation for the plugins as separate eBooks, or sell advanced examples that come bundled with the plugin for the price of one. And the most importantly, it will give easier/cheaper access to the addons for the users of C2.
I'm more ready to spend 5$ on any plugin than 29.99. With 5$ i'll buy it if it's interesting enough, store it to aside and use it when the time comes (just like steam games, probably never ). If it doesn't work as i expected, i won't be so angry. It just 5$ after all. But if it's 29.99$ i'll be careful with my purchase, and be more ready to request charge-backs if it's not what i expected.
In the end, the only thing that matters are the rules, and how clear they are. After the market is open, pretty soon we'll know all the info we need and either Scirra will adapt, and/or sellers will adapt to the new information.