Thank you for the feedback. The key addition that you get with the Explorer is access to bulk prices and bigger maps, but I probably don't say that clearly enough... you can actually buy and make maps with a free account.
My recommendation: make it as stupidly easily possible to buy a single map whenever you want, with the option for no account at all (and make it clear you can do that through your website).
I could conceivably see myself using this, the output looks really nice. But as soon as I need to sign up for an account, even if it's free..... ugh :-/
Make it easy for people like me who might be on the fence to give you my money :)
This is common with e-commerce sites. Many don't require you to make an account to add items to your shopping cart or even to check out. But if you want to make an account, they make it super easy prefilling info they already have, and they certainly won't make you lose what's in your cart.