...anyone doing 'serious research' can easily access complete full-text archives of NYT + other major newspapers by visiting either their local library (if they have a library system that is decently funded) or by visiting their local higher education institutions. Proquest and other services are subscribed to by tens of thousands of businesses, libraries, colleges, and universities, and give you access to full text complete archive of the NYT specifically.
They're protecting an investment in content, and it costs them to maintain and manage the archive and requests. $3 is high -- but it's not a major revenue stream for them. It's $3 more than anyone should have to pay, if they were wise enough to visit a library/university.