Hey zerostyle,
Welcome to The Mattress Underground! Thanks for your question.
[quote]I’m considering building a DIY mattress for myself. By doing so, it looks like I can keep prices quite low:
~ $140 for a 6" HD36 base layer
~ $299 for a 3" talalay blended top layer[/quote]
[quote]However, most of these DIY and other sites seem to want to charge $150-$200 for a mattress cover! Is there some durability/strength protection from these that I’m giving up, compared to some super simple enclosures on Amazon for $30-$50?
[/quote]
Congrats on your DIY journey 
! You’ll find lots of new friends and ideas on the forum, it’s a popular topic of conversation. To your point, there is a wide range of pricing for mattress covers, the lower end which you mention probably best suited for adding over an existing mattress cover, as you suggested. Without specific ones cited for comparison, lets look at the points you reference:
A mattress cover, also known as “ticking” maintains the shape of the mattress and helps protect the inner components from exposure to light, ozone, solvents, or other influences that can oxidize or degrade them more quickly. You can read more about the functions of a mattress cover in Phoenix’s article “Putting the Layers Together”
To quote Phoenix: “The best mattress tickings are made of a high quality woven or knit materials that are flexible, durable, comfortable, and breathable and will allow the underlying layers do the job they were designed to do. Good looking is a bonus.” I would only add that your personal preferences are important considerations, whether you sleep hot or cool; whether “natural” materials important to you, etc.; there are more considerations in the article"Your Sleeping Style, Preferences and Statistics"you may find useful.
Cotton is likely the most budget-friendly material. But budget aside, what “feel” are you going for? Something smooth? Something with minimal quilting? Something with plush, heavy quilting? Just for fun, I searched Wayfair.com’s site, they have 272 mattress covers under $50, you may want to look at the variety of types of quilting and quality in addition to what the cost is at that price point, you may find the value you are looking for among the many choices here.
Finally, some questions for you: who are you purchasing your components from? Based on your build above, did you get a recommendation for appropriate covers and if so, what materials/ price range were they? What size mattress, and what is your budget for a cover? Looking forward to hearing more as you have updates, keep us posted 
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Thanks,
Sensei
! You’ll find lots of new friends and ideas on the forum, it’s a popular topic of conversation. To your point, there is a wide range of pricing for mattress covers, the lower end which you mention probably best suited for adding over an existing mattress cover, as you suggested. Without specific ones cited for comparison, lets look at the points you reference:
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