There are multiple options for the prices/costs maintenance:

1. You can use Vendor Prices (AP202000) or Vendor Price Worksheets (AP202010) forms to maintain vendor’s prices (regular, promotional, temporary (with expiration date), price by warehouse, etc.). The Vendor Price Worksheets (AP202010) form even allows you to use simple formulas (like the calculation of vendor’s new prices based on MSRP, Last Cost, etc.)
2. MSRP and Default Price are mostly about sales prices (not vendors’ prices). For the maintenance of the sales prices the following screens can be used: Sales Prices (AR202000) and Sales Price Worksheets (AR202010). On these screens you can manage sales prices (not Default Price and MSRP). The Sales Price Worksheets (AR202010) form allows to use simple formulas (like the calculation of sales prices based on MSRP, Last Cost+Markup%, etc.)
3. If you really need to regularly update the Stock Item’s attributes (MSRP and Default Price), you may use the Import by Scenario (SM206036)/ As an example, you can take Import the IN Stock Items import scenario from Sales Demo dataset (it can be optimized by excluding multiple unneeded fields from the update).

It would be nice to be able to schedule an update to the MSRP and Default pricing like you can set the effective date for a cost change in the Item record.  It would also be nice to be able to upload a change list, similar to the sales price worksheet to alter the default and MSRP prices on the item record.

@JSager76 - these sound like ideas worth adding to the Ideas page for Distribution? 

https://community.acumatica.com/ideas

Just did - Additional pricing management capabilities - thank you!