Sure! Let's break down the problem and create a test case generator for "G: Quest of Merchant".

### Problem Statement Breakdown
- **Input:**
  - \(N\) (number of towns)
  - \(M\) (number of different products)
  - \(W\) (maximum weight Rabbit can carry)
  - \(T\) (total available time in minutes)
  
  - For each product:
    - \(S_i\) (name of the product)
    - \(V_i\) (weight per unit of the product)
    - \(P_i\) (selling price per unit of the product)
  
  - For each town:
    - \(L_i\) (name of the town)
    - \(X_i\) (x-coordinate of the town)
    - \(Y_i\) (y-coordinate of the town)
    - For each product sold in the town:
      - \(R_{i,j}\) (name of the product)
      - \(Q_{i,j}\) (quantity of the product available)

- **Output:**
  - The maximum profit Rabbit can earn in \(T\) minutes.

### Test Case Generator

The generator will randomize the number of towns, products, weights, and coordinates. We will ensure that all inputs are within reasonable competitive programming constraints.

Here's the Python code to generate such test cases:

```python
import random
import string

def generate_random_string(length=5):
    return ''.join(random.choices(string.ascii_uppercase, k=length))

def tcgen():
    # Constraints
    MAX_N = 100
    MAX_M = 50
    MAX_W = 1000
    MAX_T = 10000
    
    N = random.randint(1, MAX_N)
    M = random.randint(1, MAX_M)
    W = random.randint(1, MAX_W)
    T = random.randint(1, MAX_T)
    
    # Products information
    products = []
    for _ in range(M):
        S = generate_random_string()
        V = random.randint(1, 100)
        P = random.randint(1, 1000)
        products.append((S, V, P))
    
    # Towns information
    towns = []
    for _ in range(N):
        L = generate_random_string()
        X = random.randint(-100, 100)
        Y = random.randint(-100, 100)
        town_products = []
        num_products_in_town = random.randint(1, M)
        for _ in range(num_products_in_town):
            R = random.choice(products)[0]
            Q = random.randint(1, 100)
            town_products.append((R, Q))
        towns.append((L, X, Y, town_products))
    
    # Format output
    input_data = f"{N} {M} {W} {T}\n"
    for S, V, P in products:
        input_data += f"{S} {V} {P}\n"
    
    for L, X, Y, town_products in towns:
        input_data += f"{L} {X} {Y}\n"
        for R, Q in town_products:
            input_data += f"{R} {Q}\n"
    
    return input_data

# Example of generating a test case
print(tcgen())
```

### Explanation
- **generate_random_string:** Generates random product or town names.
- **tcgen:** Generates random values for towns, products, and their attributes, and aggregates them into a formatted input string.
- **N, M, W, T:** Randomly chosen within set constraints.
- **Product details:** Randomly generated names, weights, and prices.
- **Town details:** Randomly generated names, coordinates, and associated products with their quantities.

By running `tcgen()`, we get a test case formatted in the required input format for the problem. Each run will generate different test cases, suitable for thorough testing of the solution.