If you look at the cost of a DVD player when they first came out - and how much you can pick one up for these days, with chinese manufacture - probably about $450 and change
$6,000,000 in 1973 is equivalent in purchasing power to about $40,428,378.38 today, an increase of $34,428,378.38 over 50 years.
That’s just the inflation. That’s only if you want him to be as good now as he was clear back in 1973.
As you mention that’s 50 year old technology and special effects. And man, some seriously old threads. Lose that red tracksuit. Spend at least a million of that in a cool updated wardrobe. And super strong Pistorius legs. Each limb costs between $15–18,000 USD.
Probably more of a terminator like arm and some cool features more akin to Robocop. More badass features like a processor that would be able to scan the horizon for threats. And being able to repair minor injuries on the run. That kind of improved sci fi tech ain’t cheap.