:) Ironically there seems to be a problem with Avid running on the Mac Pro 2013 model and maybe a classic Mac Pro might get round that.Selling A Phone? Find What It’s Worth › MacBook Pro Price Factors Accessories can net an additional $10 to $20. I wonder if Hollywood film studios might be interested in your Mac Pro. However now that there is a successor to the classic Mac Pro people may be holding out for the new Mac Pro 2019 model due out I believe in October. This itself would not (and does not) prevent Catalina working but Apple are believed have taken the decision not to support Catalina on chips that have this problem. Note: Apart from the age making it logical for Apple to stop providing OS upgrades the real reason is believed to be down to the fact that Intel have decided not to provided a microcode fix for a security bug in the Xeon CPU chips used in the classic Mac Pro models.

macOS - officially it can be upgraded to Mojave, unofficially it is possible to do Catalina.

Blu-Ray - should you desire it you can fit an internal Blu-Ray drive.

WiFi/Bluetooth - you can replace the original cards with one that does 802.11ac and Bluetooth LE aka 4.0/4.1 which will support Continuity and Handoff features.

USB - you can get a USB 3.1 with type C connectors PCIe card - not even the Mac Pro 2013 can do that.

SSD - you can get a PCIe adapter to fit NVMe SSDs and can get fantastic speeds.

MacVidCards are now doing a 'flashed' AMD Vega card which works with Mojave and potentially Catalina

Video card - can be upgraded but Mojave does not support newer Nvidia cards, High Sierra can use newer Nvidia cards.RAM - can be upgraded all the way to 128GB depending on configuration.Many aspects of your Mac Pro actually can be upgraded - some make more sense than others. This is way beyond the trade-in threshold of any company. The (classic) Mac Pro was discontinued in 2012 making your model around seven years old.

Apple macbook pro 2011 trade in value