That axle listed on Ebay has a good price, but it didn't show the shipping cost.
Also you want to make sure the dimensions for wheel width & brackets that mount it to the frame are right.
Northern Tool lists an axle like that for $225. Would have to check dimensions.
I presently need to replace the axle on my 16' Casita
. Factory wanted $529 + $150 shipping to Houston, or $90/hr (4hr) to install. I found a trailer place locally that wants $369 for the axle, and install @ $65/hr. I plan to have them do it if they can promise not to burn down the trailer from welding sparks.