Newegg offers the Western Digital Blue 4TB Serial ATA 6Gb/s 3.5" Internal Hard Drive for $99.99. Coupon code "EMCTUUU24" cuts it to $84.99. With free shipping, that's tied with our October mention as the lowest price we've seen. (It's the best deal now by $15.) It features a 64MB cache.
Before you spend another dollar on items and services like these, check with your public library. You will likely be surprised by what it offers for free.