The products you sell to restaurants are freely available online, or cheaply available everywhere pretty much (video promotions, online ordering, online reservations etc.)
Its just commission. So unless you already know alot of restaurant owners, you will not earn squat busting your hump up and down the restaurant areas.
Without any unique products to sell, there is little reason for a restaurant owner to switch from their current marketing company to dotmenus.
Their prices are cheaper sure, but you get what you paid for. Business people know that very well.