users expect high quality games for a few cents
Expectation is the key here. Thinking of games as a commodity, the consumer is now presented with a staggering amount of choice and I think we're seeing a situation where supply outstrips demand by considerable margin. Therefore, unless the item is of perceived scarcity/value, it's likely a cheaper (free-er) alternative will be available so we've learned to go find it.
Added to this is the key problem with the web: it was not designed as a paid content delivery platform. iOS was, droid wasn't, etc and it shows.
The users of the "desktop" web do not expect to pay for content so this IMHO presents the biggest problem for HTML5 games.
My suspicion is that HTML5 games that will be able to 'monetize' effectively won't be casual games. They'll be hybrids of free to play / subscription based models using well known I.P. e.g. a Fallout universe based MMORG over HTML5