Are you planning on building it yourself, or is this a pre-build you're after? Assembling it yourself will be cheaper, but I'm guessing that you haven't built one in a long time, if ever. There are companies who offer "off-the-self" PC builds, as well as more custom-built machines that you can build in a configurator on their website. The two that I've purchased from have been
Overclockers UK and
PC Specialist. Both of those companies can do Intel-based or AMD-based builds. I've been an Intel guy since the beginning, but AMD's prices are occasionally tempting, and would doubtless be helpful in helping you stick to the budget.
I suggest you play around with PC Specialist's AMD configurator, as their prices seem a bit better than Overclockers, and the configurator is more user-friendly.
Here's the list of minimum, recommended and optimum specs for MSFS2020 for reference.