An r720 from dell or similar model from dell with 600GB*2 SSD intel s3500DC model, 20 cores & 256GB of RAM will go for 5k-7k. You can bump this to 386GB of ram without going above 10k.
If you are looking for larger purchases 50k+ USD than you should talk directly with Dell, HP or comparable vendor and put them into the play off for who you choose :)