Windows 10 available through official stores and retailers.
Yes, purchasing Windows 8 and upgrading would be a viable option.
Sure, just clarify what you mean by "8.1 not 8."
Purchase Windows 7 and then upgrade it for about $6 less.
They don't offer Windows 10, or maybe the price is prohibitive.
It's more affordable to purchase a previous Windows version that meets the eligibility for a free upgrade instead of paying the full price.
Too costly is the issue.