Just a few days ago, a listing for the Ryzen 5 3500X popped up on Newegg.com (opens in new tab) for $269.99. It is imported directly from Hong Kong by an e-retailer called Corn Electronics (opens in new tab). If you want your very own, make sure you get it fast as this listing expires on September 17. The Ryzen 5 3500X launched nearly a year ago featuring six cores and six threads, a 3.6GHz base clock, and a boost clock of 4.1GHz. Unfortunately, the 3500X was limited to OEMs, and being a China-only exclusive made it almost impossible to get your hands on one. The actual MSRP is unknown due to it being an OEM SKU; however, a year ago, you could grab it for $154 on some Chinese retailer sites.
We reviewed the Ryzen 5 3500X several months ago and praised it's overall good performance for the price (we paid $190 for our sample on the grey market). Its lack of SMT made it a solid gaming CPU at the time, handily beating out the Core i5-9400F in several gaming titles. However, it's lack of SMT means it is severely hampered in threaded applications. Should you buy the 3500X today? Unless you're a CPU collector, definitely not. For the price of $269.99, it isn't competitive in any way, shape, or form. For context, AMD's new Ryzen 5 3600XT is $20 cheaper than the 3500X listed on Newegg.com. Unfortunately, Corn Electronics probably had to inflate prices to cover shipping and other costs related to importing this unit to the United States. If the price was more ideal at $150, I bet it would make a great CPU for budget PC builders, especially when the 3500X's closely related brother, the Ryzen 3 3300X, is nowhere to be seen on store shelves. Again, if you want a 3500X as a collector's item, grab it soon as the listing will only last until September 17.
Yes, motherboards should support the 3500X because its an official AMD SKU. However, I'd check your motherboard manufacturer's website for actual CPU support to ensure compatibility.