What do investors actually pay for a list of driven addresses?

The two models aren't the same product legally and that's most of why both exist. A flat fee for data is a data sale. A payment contingent on a closing is compensation tied to a real estate transaction, and in a lot of states that's the exact fact pattern the brokerage licensing statute describes, regardless of what you call yourself. Whether it catches you depends on your state's definition and on how the agreement is written, so that one goes to a real estate attorney licensed where you'd be working before you take a dollar, not after.

Separately, read what you'd be selling. A raw address is worth very little because the buyer still has to pull the owner, skip trace, and mail. What has value is the address plus a dated photo plus a specific note on what you saw.

I'd be on the buying side eventually, and I wouldn't pay a dollar an address for a list of streets. I'd pay for the note. "Boarded rear window, two years of leaves in the gutters, no vehicle, photo attached, driven on two separate passes" is a different product from a spreadsheet of addresses.

Price per verified record rather than per address if you can stomach the extra work. Once you've matched the parcel to an owner name and a mailing address, you're selling something that can go straight into a mail merge, and that's where the 75 cents to two dollars a record range lives. Raw sightings with no owner match sit way below that. Watch your match rate though, because if you're paying a skip vendor per lookup on records that don't hit, your cost per sellable record isn't the same as your cost per lookup.

Sell the same list to five investors and that owner gets five letters in a week and calls none of them. Exclusivity is the whole product and it's the thing that's hardest to price.