But, why using a free service if you're planning to work on a project? Why having to be dependent from quick and rough solutions such as blockchain.com's API? By setting up a node it'll come cheaper than you may think. Then you could install a script like
mempool.space's and enjoy the development with no third parties needed to trust. (The open-source project “mempool” comes with its API, if I'm not mistaken)
It depends on your budget. Ofc it is much better for privacy, trust, etc to run your own full node in a cloud server and create your own API. But this requires a deeper knowledge (to set up the backend and the server) and budget.
Using free API is free. If you are doing all that, I think you may spend about 20-30 USD per month at least.
I believe most of cryptocurrency projects survive on donations. Unless OP is going to make a commercial project which has a good potential, he can just use free API...
For example, blockchair API have a limit of 1440 requests per day for free
Blockchair was free all that time? I thought you could only use if you paid. (which also comes with the premium features)
As far as I know, they always had a free version.
You can use other good free api as well. Personally, I have used in my website mempool.space, sochain, blockchair.com, and others over the last year. Recently, I have been using only mempool.space, bitcoiner.live and Coindesk API and never had any problems. I have about 45k visitors per month, which is more than 1500 requests per day on those API (as sometimes I make about 1 request per minute or 30secs depending on the page).