The calculated price is different than what I am expecting based on the cost and the percentage I've selected
You may have the incorrect setting in Preferences that enables or disables the parts markup formula.
If you take a part that costs $10.00, and use the markup formula and 30%, you get $14.29. If you take off the 30% of 14.29, you get back to the original $10.00. Without the markup formula, you would lose money. $10.00 with 30% markup (no markup formula) = $13.00. Then 30% back off gets you $9.10.
How to change it:
You can disable this in View > Preferences > Parts tab > More Options… tab > “Do Not Use Markup Formula”. Note that existing work orders have this set (from main W/O screen > Options > View Options > Pricing Info tab) and so do existing OTC invoices (from main OTC invoice > Billing Info > Pricing Info tab).