Find a different shop. If they are trying to charge you to fit a boot your buying that is not right. However if you were never going to buy the boots from them, they can charge you that.
Overall it sounds like the SPK may be too low in the instep for you. Its a pretty low boot. As for your toes a footbed will help that but it will usually raise your instep so make that worse.
Maybe try the Overlord, similar fit to the spk but higher in the instep.
But overall try to find a better boot fitting shop and make it clear you want to buy boots and footbeds from them from the outset.