Speaking as someone with no practical knowledge:

If you cant afford to run a high pressure ram, look at a low pressure (possibly larger bore) one, but bear in mind the price of the regulator, buffer tanks, etc.

If thats not going to work for you, have a look at an electric lifter? You can probably make one of those for less (unless your names Ed or Carlo), and itll be safer.

To make your own ram, start with a decent lump of steel, the metal lathe you obviously have, a good knowledge (I recommend a degree course) of fluid dynamics and a load of moderately specialist components to make the plunger, seal, end caps, etc. Dont forget to make two so that you can destruct test one and get a pressure rating. Try not to autodarwinate while doing it. Oh, and dont get it wet. In other words: best of luck, but of all the reasons to make your own ram (or at least, get one made - talk to the Bulldog Breed team to find out who they used?) saving money is unlikely to be a practical one. Economies of scale amongst people who know what theyre doing, and all that.

Sorry to be harsh - Im just trying to impress on you not to try to do this.

Alternatively, hang around in the for sale section and save up (preferably not in that order). Which is approximately what Im doing. :-)

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Fluppet