We all know that bitcoins price changes quickly because of its demand So if some online shop sells products and pricing it in bitcoin,
How can we price it ? Should the price change also like btc?
Most of the online store or merchants use third party payment gateway like bitpay to accept bitcoin which will be converted instantly into USD so that they will not loss due to price volatility of bitcoin.
Those payment gateway also provide simple api/merchant tool which will automatically calculate bitcoin according to price of the product, so actually amount of bitcoin to be sent will change according to market price of bitcoin.
so it is good to use the third party service to avoid loss money because of unstable price of bitcoin.
but if you do not want to use the service, you can go yourself updating the price of your stuff. it would need you to stay in front of your computer in almost all hours of your day.
the other option is you can keep the price even bitcoin price changes.