Licence costs are available from MicroSoft's site. I don't know if you can still get new licences, SQL 2008 R2 has entered it's last leg of support.
The web hosting company can advise whether they will provide the licence, and what their fees will be, or what licence they offer as alternative. Shop around, this is expensive.
Check what version of SQL you are running on, if your database is functioning at 3x the maximum tolerance, I doubt you are actually running on SQL Express.
SELECT SERVERPROPERTY('Edition') Edition,
WHEN 1 THEN 'Personal or Desktop Engine (Not available in SQL Server 2005 and later versions.)'
WHEN 2 THEN 'Standard (This is returned for Standard, Web, and Business Intelligence.)'
WHEN 3 THEN 'Enterprise (This is returned for Evaluation, Developer, and both Enterprise editions.)'
WHEN 4 THEN 'Express (This is returned for Express, Express with Tools and Express with Advanced Services)'
WHEN 5 THEN 'SQL Database'
, SERVERPROPERTY('ProductVersion') ProductVersion