I honestly think that there are two types of wholesalers. The one you mentioned above and another that is more honest. People don't value transparency like they should. Especially when your dealing with the buying and selling of property, full disclosure should be given. It's a respect thing!
I also believe that a wholesaler who does not make their intentions known is someone who is afraid that the information may interfere with the sale. In all honesty if you're a good salesman people will want to partake in transactions with you because they like who you are. Numbers do play an important factor, but no one wants to buy ANYTHING from someone they don't trust, not even a piece of gum.
All in all, I believe the wholesaler adds value to a transaction because in all honesty, investors don't have much time to source leads and nurture them, etc. That's why you have thousands of investors sending out a ridiculous number of letters each week, because they don't have the time it takes to truly nurture a lead so they do what they can with what time they have.
The wholesaler comes to you with a done deal. Yes it may be more expensive than if you found it yourself, but guess what you didn't find it yourself, because your time is worth MORE than that. You're paying the upsell price for convenience. Find a wholesaler you can trust, not just someone who woke up one day and say "Hey, i'd like to buy property today."