As far as I know, the industry standard is the Lawrence Berkeley National Laboratory's annual 'Tracking The Sun' report[0]. I recommend it as a great primary source - the measurements are well explained and accompanied by helpful charts and analysis of the year-to-year changes. LBNL also publishes other useful resources on energy production/consumption, so it's worth browsing around to see what they have if you're interested.
You have to read a bunch of news articles and keep an eye out for articles that actually include numbers. I don't know of any public databases aggregating that sort of information. There are commercial services that sell data and reports.
Keep in mind that solar electricity, like any form of electricity generation, has location-specific and project-specific cost factors. Building any form of power plant is cheaper in China than in Germany. Solar power prices in Nevada are almost always going to be cheaper than in Michigan, because even if the construction costs are the same, the arrays will get more sun per year in Nevada.
If you want to check solar energy prices for your _home_, then I'd recommend EnergySage (https://www.energysage.com/). I think they have a tool for commercial buildings as well, but don't quote me.
If you want more generic public data, I think other commenters have better sources, though their blog might have some articles wit that information.
