First off... I'd read this thread if you haven't already...
https://www.thegearpage.net/board/index.php?threads/288817
The materials to pack an amp like that are fairly expensive... but
better to have the amp arrive in good condition... the carriers won't
pay off insurance claims if you throw an amp into a box with some loose
foam and wads of newspaper. (I did receive an amp packed like that...
luckily, there was no damage.)
I had a local "Mail & Business" pack one of my amps... total
packing/shipping cost was $128. But the amp got there unharmed and the
buyer said it was the best pack job he'd ever seen, so... I, in the end,
was a happy camper, even though the packing/shipping charge was so
high.
I've packed amps for shipment on my own... if the amp is smaller... it's
not too hard, but I tend to go overboard, packaging for a 30 foot drop
off the carrier's conveyer belt. Double boxed with hard foam in the
inner box, then peanuts in the outer box. Crazy? Maybe...
Anyway... it seems that it always cost more than I anticipate to ship
amps. 54lbs? It's going to weigh more than that after it's been packaged
up...
at least another 5 lbs and maybe as much as 10lbs, depending on
how it's packaged.
I would figure on spending $100, at least, to package
and ship the amp. More if you have someone else package it.
That's just my two cents based on my own personal experiences shipping
amps. Not saying I'm "right" or anything... just sharing my experiences.