If you are seeing one price listed for a design, the price may increase after clicking on the design to view it.
This is because you are seeing the price on the preview that applies to the basic purchase of the design -- without any SVG or Commercial License option added.
You may have enabled the option on your account to add SVG files if they are available. This can be toggled on or off in the 'Download Preferences' section of your account. You can also simply check or uncheck any purchase options to add or remove them prior to adding them to your cart, or you can make adjustments from your shopping cart to toggle purchase options on or off.