We do not yet know anything concrete about Yuan purchase by Bangladesh or Chinese govt. offering it to us. News is still unconfirmed.
However average Yuan class price for export in quantities of three to eight will be way over $350 million per sub with support, spares, maintenance etc. You are not just buying 'a' sub, the specialized support, expertise for repairs and maintenance has to be bought too, uncharted territory for a lot of countries like Bangladesh. Plus there is always graft for the big wigs....
The news that Pakistan was buying Yuan class export version (Also called Type 041 locally in China or S26 for export) with ToT was reported in the Pakistan section quite a few years ago. Since then Pakistan Govt. confirmed it again late last year. Pakistan's deal is valued at $4 to $5 billion for eight subs. Source,
http://thediplomat.com/2016/08/chin...with-8-new-stealth-attack-submarines-by-2028/
Thailand bought three export Yuan class (S26T) subs at package price of US$1 billion. Source,
http://www.defenseworld.net/news/16...hree_Chinese_Subs_For__1_Billion#.WHCcx_krKM8