How do I know if these are good prices on perfume?

I found this awesome site for perfume, and they have they best scents like milk chocolate, and cotton candy, marshmallow, pink lemonade... and the list goes on! but im usual not a perfume buyer so I dont know when somethings a good price and when somethings not! they have some EDP perfume roll-on 10ml for like 6.99, and some perfume oil roll-ons .3oz for like 7.75, and some silky body mist 4oz for like 7.00, and dry oil perfume 1oz for like 7.95! I have no idea if any of these are good buys or if there not can anyone help me out?!?

its cheaper than walmart, so I think its a great deal.

They sound like good buys to me.