Office 365 Licensing

Our organization is migrating to O365.  We have about 650 users.  300 are back office and will receive an E3 license.  50 more are just email users and the rest (300) just need to access our internal, future SharePoint site.  For the 50 email and SharePoint only users, we are planning to put them on a K1 license.  The problem is the 300 users who “might” visit our internal SharePoint site.  My understanding is they all need a license to access the site.  A few months ago, a SharePoint Plan #1 license was $3 per user and now it has changed to $5.  These 300 users will rarely, if ever, access the site, but we need to assume they might.  However, $1500 a month for this is beyond steep.  Most of these 300 users will be using a shared computer as they are warehouse workers.  However, some may want to access our internal Intranet from their mobile phones or home connections.  It is not a top priority, but we would like to run analytics to see who is accessing the site.  If we used a shared login for these users, we would lose that ability.  Any advice on the best way to handle this is appreciated.