Create a generic non-inventory sales part called pricing correction or something similar.
Use that part to charge the additional amount (this would only work if you’ve undercharged the customer). This would eliminate the need for the RMA and the inventory transactions. The standard price would be set to 1, 10, or 100 and then could either be over-ridden to the difference needed or if you don’t want users changing the price on the customer order, use the quantity field as a factor times the standard price. 4.3 x 1 would be 4.30, or 4.3 x 10 would be 43.00.
If you’ve over-charged the customer, just issue a credit invoice for the difference.
A better way to do this for purely price adjustments is to create a correction invoice. These can be used for an over charge or under charge and the correction invoice does not require the RMA and a new customer order to re-invoice.