I have thought of this same thing many times. Giving up to save money.
My 75G is costly, the RODI filters clog way more than I thought they would and MH lights are expensive, electric bill... woooo boy!
If you still like the aquarium.. I agree. go to the LFS and ask if they will store credit you for some of what you have... kepp a sand bed and all going.. trade in your Corals for the lights, consider fish only or FOWLR. you can cut the lighting down.
I'm looking at my Xenias supporting my whole tank right now. I found a place that will give me store credit for attached Xenias... I can't slow them down... the trade in value stinks, but I have more xenias than I can use, and need new bulbs too. So I make my own rocks or buy blanks dry rock.. let them grow onto whatever I got zip a little more store credit.. they mark way up make money, I keep my tank healthy.