Are there any construction sites of new houses around you? There are often scraps of wood in the dumpster that can be used for smaller projects like yours. Buying a sheet of plywood and cutting it (or having the store cut it) into usable pieces would be a lot cheaper than $50.

There's big plastic "storage tubs" that are a lot less than $50. If you're in an area with a farm store, you might find a feed or water bin to suit your needs for a lot less.

A baby pool or trash can.

I've made a couple small-medium sized planter boxes from pallet boards (free).

Maybe your town has a warehouse district where folks receive stuff in crates? Some places pay to have this stuff removed.

The Lowe's and Home Depot's around here have scrap trash cans inside the store in the lumber dept. They are scraps from cutting wood to order. They are free for the asking. Sometimes you can get something like that at a yard sale. We bought a large quantity of old windows and screen doors for just a few bucks. The man was happy to get rid of them!

I have seen large planters made out of filing cabinets. You remove the drawers, put the cabinet on its back, paint, line with plywood/scrap lumber.

Here is a link that might be useful: Filing cabinet planter

I am trying a cardboard appliance box (from a dishwasher) this summer. I put compost-ible materials on the bottom, left the corner bracing (heavy cardboard "spines") in place, put it on a pad of thick clay tiles and added soil. Lots of soil :) lol. Then I wrapped the entire thing in a long length of burlap and tied that tight with several lengths of baling twine. I bought a roll of that so it cost me $10 but I have a lot left too. It looks nice as well, natural and fits in out there. So far so good, I understand they should hold up for one season, we'll see! If it works, I'll find a way to do about a half dozen of these next season - they are giant and I'm thinking if I wrap in carpet remnant or even old tarps and then the burlap, they might hold up for a few years like that.

There's a magazine published called Flea Market gardens that is a good example of what some of you are discussing. I find it on the newstand, at the magazine racks in your grocery stores, and drug stores. I hope that they will offer mail subscriptions of it eventually. One of the covers was where somebody painted up an old dresser and used the drawers for planting flowers in them. I recall where one gardener took a dresser drawer out and made a flowerbed out of it.