You can see the new prices here:
https://www.usps.com/new-prices.htmCtrl+F for 'Priority Mail' and such.
Priority, paid on-line, which I think is "commercial base":
"Flat Rate Envelopes 5.05
Legal Flat Rate Envelope 5.25
Padded Flat Rate Envelope 5.70
Small Flat Rate Box 5.25
Medium Flat Rate Boxes 11.30
Large Flat Rate Boxes 15.80
APO/FPO/DPO Large Flat Rate Box 13.80"
Priority paid at post office:
"Flat Rate Envelopes 5.60
Legal Flat Rate Envelope 5.75
Padded Flat Rate Envelope 5.95
Small Flat Rate Box 5.80
Medium Flat Rate Boxes 12.35
Large Flat Rate Boxes 17.45
APO/FPO/DPO Large Flat Rate Box 15.45"
Slight increases.