If you want to stream all of the March Madness games at home (or at your desk) without a real cable subscription, DirecTV Now looks to be your cheapest option at the moment.
The service’s base package includes TNT, TBS, TruTV, and CBS (in select markets), which together would cover all 63 tournament games. It normally costs $35 per month, but you can get your first three months for just $10 each with promo code YESNOW3. That’ll auto-renew at the regular price after the promotional period, but you can cancel any time, including after your first month, meaning you’d only pay $10 out of pocket for full tournament access.
Alternatively, you can still prepay for three months at regular price ($105 total), and get a free 4K Apple TV, which normally costs $179 by itself. I did this myself a couple of weeks ago, and I’m really liking it.