Does one need to purchase expensive shoes for trekking ?
No. What you need are shoes with good grip on dry and wet surfaces. While most shoes will have good grip on dry surfaces, they can be extremely slippery on wet ones. You will get such shoes for about Rs. 500-600 in any multi-brand shoe-shop. Avoid buying shoes just before the trek. Use the shoes at least for a week or so before the trek. This will avoid sores and blisters during the trek.