Would or do guides ever charge a customer for trailing a guide on a lake?

Yes. Typically $100 extra.

100-150 extra

Yep, but be sure you have talked with the guide and the customer on board. Typically it's three or four buddies together with a trail boat. Don't know if I've ever heard of trailing any other way. But I'm sure it happens.

SE Kansas grass grower

I thought people trailed guides all the time. The ones with wrapped boats especially. Simply stay back at a distance and make it look like you are fishing "your own" spot, and when they leave, move in and pick up where they left off. 80% of the time it works every time. (Just kidding)

it's a good way to find there best Sand bass spots

The prices quoted so far, are pretty accurate for this type of scam. Generally trail boats end up being a way for more people to be involved and reduce the per person costs. It's a pretty common element in saltwater guide trips. IME, it works well in saltwater situation due to the amount of school that can be geographically confined in a given area. Now, on bass fishing, I'm not so sure how that would work. Much less area/concentration/opportunity, etc. than in salt water. My given inclination is its a scam to try to reduce the overall costs per trip for any one given excursion. For me personally, I'd just hire the guide that I thought (might be) somewhat better than the crapshoot you'd take on an unknown body of water if you did it solely by yourself. That's not to say that in rare given situations that this method could be productive, I suppose it could but usually, on a percentage basis, it's a low percentage shot. Think about it. How many times do you read on her about all the "hot shot" guides who "know where the fish are" and post glowing results about how they are "killing them" only to see a post by some poor smuck who booked the guide only to roll snake-eyes? It's usually covered up by bad weather/should have been here yesterday. fish weren't co-operating (insert any "excuse of the day" you can think of) etc. THe "trick" from a guide standpoint is did you give the customer "PERCEIVED" value. How many times have you read on here where a guy strikes out but yet giver glowing accolades to the guide? This generally means the guide is a good salesman and pimped the trip right and the customer bought the line. I'm not saying it's not right/immoral/whatever, it's jut the nature of the game.