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

The two models are not the same product legally, and that is 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 is 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 would be working before you take the first dollar. Separately, read what you would 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.

A buyer on the other side of this is unlikely to pay a dollar an address for a list of streets. What gets paid for is 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 well 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 part that's hardest to price.