I've been working on this exact problem and ended up building CSMarketAPI (csmarketapi.com) to solve the rate limiting and documentation issues with Steam's market endpoints.

There's a free plan that should work well for smaller projects - you get access to all endpoints including real-time listings and historical prices. If you scale up later, the paid plans are reasonably priced.

Way more reliable than trying to parse multiple HTML pages from Steam, and you get data from other marketplaces too. Check out the docs if it fits your use case!