Hello. Consider this a dummy bid until I get more details about your project.
I hope you are not considering to get this project done by just $500, it won't happen. If it's really 10,000 (ten thousand) sites, then consider you have to do a different scraper for each one, no matter how similar those sites could be.
You talk about a CMS, but with your description I see no *content* to be *managed*, scrapers will save data into DB and the front-end would be just a main input box, plus maybe some other input fields as you talk about "drop down input fields", which will query DB. So nothing to manage there.
You ask me to describe the logic steps and main components of the solution, but I only can give you a broad view, I need specific details to give you a precise answer. Also consider this FL reply box only gives me 2000 characters.
I need to know the data you want to scrape so I can choose a proper DB (SQL/NoSQL). Then I need to know a few sites, the main ones at least. And finally I need to know how do you want to present the access to this information to your users: you already told me you want to search, but what else will the site have?
In essence there will be background processes making the scraping on one side. A DB collecting data. And a front-end to allow users to search for stuff.
I cannot tell you much more than that with current description.
Thanks for reading my bid. Consider expanding you project description.