QB keeps average cost for inventory, unless you have enterprise and have turned on FIFO
stock the items, who you order from is immaterial, then sell them
I’m not sure what 10 PCs by 5 means, or
15 items with 7 USD
QB keeps inventory value in the base currency if you use multicurrency, […]
Resolution for 'cost issue: 'Adding inventory – same product, different cost different PO same vendor' available: Yes.
The cost issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the cost issue yourself by looking for a resolution described in the article. If it is a complex cost issue or you are unable to solve the issue, you may contact us by clicking here or by using other cost support options.
For more information about resolving issues related to cost in Quickbooks/QBO or to get support for the issue 'Adding inventory – same product, different cost different PO same vendor', click the link below: