Wall is about to become a max player, so the question is moot. Rondo is clearly more valuable on his present contract.
It would be really hard to gamble on the upside of a potential superstar who hasn't done anything yet against an all-star in his prime who is also a known quantity. I'm not saying Wall can't be better than Rondo, but no serious person is taking that bet at even odds.
I don't think the money value is that clear, because Rondo's contract isn't infinite. Take a look at the next 6 years, assuming Wall signs for the Max, then Rondo signs for max when his contract is up:
Current 13-14 14-15 15-16 16-17 17-18 18-19 Total
Wall $5.90 $7.50 $13.67 $14.69 $15.72 $16.74 $17.77 $91.99
Rondo $11.00 $12.00 $13.00 $14.66 $15.76 $16.94 $18.21 $101.57
Now, this year is over, so it ends up being about 4.5 million cheaper to have Wall starting next year, then if each gets the max allowable when their next contracts are up. So the question is, is Rondo going to get the max? Will he be upset if we low-ball him since he probably has been underpaid on this current contract?
Instead of the max (which is 5 years, but only looking at the first 4 years to keep it the same length as Wall's), which would be 4 years/65.57 million, he'd need to settle for 4 years/61 million or less to be equal or cheaper than wall. Would someone offer more?