Hello,
I can make this bot in python very cheaply!
I design it the following way:
-Firstly it scans the instagram page for a baseline of the posts.
-It saves the post id's
-At a variable set interval (however small you want the interval to be) it scans the last post
-It compares the id of the scanned post with the last saved post
-if they are diffirent, it does whatever you want it to do (notify you, save the image, ect...)
This bot could be used on an infinite amount of accounts.
If you have any further questions, please let me know!
I look forward to working with you!