$400 is spendy for a 16550A.
It certainly is in this country but probably not where the OP lives. And shipping is going to cost a bundle so if that's included then it's probably a heck of a deal! FWIW I don't think you could even give away a 16550A in this country any more.
A 16550A is a 102-channel / 6 POD, 100MHz state / 500MHz timing logic analyzer module. The sample depth is only 4K samples per channel, or 8K samples per channel in half channel mode.
The mainframes are the 16500A which is floppy only, and the 16500B and 16500C which have hard drives for booting and storing configuration and data files.
A good thing about a 16550A module is that it is compatible with 16500A, 16500B, and 16500C and also 16700A, 16700B, 16702A and 16702B mainframes. If you started with a 16500A mainframe you could move a 16550A module to a newer mainframe later. A 16500A mainframe is not compatible with 16555A 1M sample per channel modules. Basically the only good thing about a 16550A module is it's the module you probably want if the only mainframe you have is a 16500A mainframe. In most cases there is probably a huge difference in usability between a 4K sample 16550A module and a 1M 16555A module.
In my opinion for whatever it is worth the best uses of a 16500A mainframe or a 16550A module are as spare parts for newer mainframes and modules. I would want at least a 16500B or newer mainframe.
As far as giving away 16550A modules, I wonder about that myself. I have several and figure it might not be worth the effort to try to sell them on eBay. I could probably get more by removing the POD pair cables from the modules and selling those separately.
If you were looking at shipping something to Chile, an HP/Agilent 16500-series or 16700-series would be very expensive due to the size and weight. An HP/Agilent 1660-series or 1670-series is slightly smaller and lighter, but would still be expensive to ship there.
For Tektronix, I wouldn't want to ship a TLA711 mainframe. Those are even bigger and heavier than an HP 16500-series mainframe, but if you can find an affordable one local to you that you don't have to ship that might be an good option. It would be better to upgrade to a TLA721 controller.