How to build 4g LTE base station in very low cost

Refer to:
1. https://cyberloginit.com/2018/05/03/build-a-lte-network-with-srslte-and-program-your-own-usim-card.html
2. https://cloud.tencent.com/developer/article/1684051
3. https://blog.white-alone.com/%E4%BD%BF%E7%94%A8srsLTE%E6%90%AD%E5%BB%BA4G%E5%9F%BA%E7%AB%99%E7%94%A8%E4%BA%8E%E6%97%A5%E5%B8%B8%E6%B5%8B%E8%AF%95/
4. https://www.white-alone.com/%E4%BD%BF%E7%94%A8BladeRF%E6%88%96%E8%80%85B210%E5%BF%AB%E9%80%9F%E6%9E%84%E5%BB%BA4G%20LTE%E6%B5%8B%E8%AF%95%E7%BD%91/
5. https://www.mobibrw.com/2018/10729/comment-page-1

USRP N210 Taobao price 26000 RMB = 4030 US$
https://world.taobao.com/item/530598387626.htm

Some people may think N210 is too expensive.
USRP B210 transparent version 500 RMB = 714 US$
https://item.taobao.com/item.htm?spm=a230r.1.14.30.6ea326b6S8jv4c&id=618435712984

Bludrive IISIM card writer 360 RMB = 56 US$
https://world.taobao.com/item/573989554039.htm?spm=a21wu.11804641-tw.0.0.2ab14425CoYRBi

MCR3512 140 RMB = 22 US$ (If you think Bludrive IISIM is expensive)
https://world.taobao.com/item/591994964214.htm?spm=a21wu.11804641-tw.0.0.2ab144251mduQO

Test white card 30 RMB = 5 US$
https://world.taobao.com/item/613889161598.htm?spm=a21wu.12321156-tw.0.0.3f2f4d5029U0h8

Software SDR LTE on ubuntu free = 0 US$
https://github.com/srsLTE/srsLTE

USRP Hardware Driver (UHD) free = 0 US$
https://github.com/EttusResearch/uhd
USRP binary Installation
https://files.ettus.com/manual/page_install.html

Total price = 741 US$