How to maintain the same profit after gst

Proprietorship. Deals in electronic goods such as bulbs,socket etc. Retailer. if they opt for composition scheme they will not get input credit. so for them cost of purchase will increase and that will result in reduction of profit.Moreover they are not allowed to charge tax from customers. 1.In the one hand their cost will increase. 2.On the other hand they will have to pay 1% of annual turnover as tax by their own pocket . What benefit should the retailer seek from wholeseller to maintain his profit same as before GST .