So, yes maybe the legend does draw in tourists with their money - but there was far less deliberate targetting of this than I would have expected.
I've done the length of the loch a few times on a motorbike, usually along the A82 which runs along the north west shore. I have once done the length along the south east shore, which often takes you further from the water, but higher up, so you get a completely different view. There are places where you can easily get to the waterside, though — and who could resist watching for a few minutes, just in case... ? A favourite view is from the very end of the loch (SW end) where you can get to the water and look straight up the Great Glen. Magnificent.
It's not easy to see how they could exploit the monster legend more than they do. There is nothing that they can show you. Therefore, you get the Loch Ness Centre and exhibition, and a few signs, menus and the like which might refer to the monster. No doubt you can have small, medium or "monster" portions in some of the cafés, and no doubt someone does a "Nessieburger". You can get "Nessie" furry toys and tee shirts almost anywhere in Scotland.
Very few people would go to the Loch to sit for hours in the hope of seeing the monster. Those who would are perhaps the least likely to be interested in the full "tourist experience".
On the other hand, what a fantastic place for anyone who is interested in fishing — and such people are often well heeled and able to contribute lots to the local economy.
What has always surprised me is how few leisure boats you see on the loch, compared, say, to Windermere.