Sales is not the only growth metrics for valuation as margins are going to increase. The new models seldom have discounts. The higher variants usually have margins in excess of 40% and the spares often have even higher margins. For every vehicle sold today, the sale of spares contribute for the lifetime of the product and often increases with age. This causes multiplier effect.
The growth of cab industry has pushed Dzire to become the new Indica of cabs. The running cycle for these cabs are very high and the service and spares over time will be much higher than personal use.
Altogether I feel we could see bottomline growing much faster than topline. This if you look at PE, the stock is fairly valued, if not undervalued. The capacity constraint is one big hurdle now and it will ease over time. This means they can increase sales growth even further from 2020.