There isn't going to be a nice numerical value that you can assign to surveil like you can to scry because the utility of surveil depends on your deck.
If you have a deck with no graveyard interaction, surveil is pretty much identical to scry in terms of card advantage. It's arguably worse, because moving the cards to a public zone gives your opponent information about what cards you want in your hand, makes the cards vulnerable to graveyard interactions your opponents might have, and makes it slightly easier for you to deck out (all of which are pretty minor).
On the other hand, if your deck has graveyard interaction, surveil suddenly jumps in value. Discarding a card with flashback or jump-start gives you half the value you would have gotten from drawing it. Surveiling a Narcomoeba is actually significantly better than scrying or even drawing it. And a deck with undergrowth becomes more powerful with every creature dumped into the graveyard.
All this makes the 'value' of surveil significantly more variable than the value of scry, and significantly harder to analyze.