The configurator, the presets on the home page, and the checkout page all run the exact same pricing function. Nothing is recalculated differently between pages.
vCPU, RAM, and storage are each priced per unit. Move a slider and the total updates immediately, before you commit to anything.
Every surcharge, whether it is Xen, Windows licensing, cPanel/WHM, extra IPs, backups, or managed support, shows up by name in the summary.
Switch to annual billing and a flat 15% comes off the monthly rate, shown as both a lower monthly figure and the amount due today.