Look at the string-draw (or whatever they call it) solar cell manufacturing technique.  Hasn't kept it off the market, from dropping the price to below that of panels with cells sawn from ingots (though it IS far above where it's likely to settle once the patent runs out).

Patents give the inventor and his backers - or whomever he sold the rights to - the opportunity to milk the market enough to make up the startup costs with a healthy profit and ramp up production.

While the patent is in force they get to set the price they want.  But they're not immune to competition - just to competition with the SAME technology.

If they're not too smart they'll price it enough below the competing technologies to steal market share from them while increasing the total market only a little.  If they're really smart they'll go for fast nickles rather than slow dimes (perhaps after a little stealing-and-milking), and price it low enough to enter new applications or shift the economics on existing ones (like cogeneration or substitution for grid connection), causing the market to expand explosively and capturing it all - licensing the technology if they can't meet the entire demand themselves.