If you really wanted to save money, you could use the CPU to generate the display. Many older machines did that, notably the Sinclair ZX80.
Essentially all you need is a memory mapped buffer chip and an R2R DAC made of passive resistors, and then some output buffer op-amps. Possibly some kind of encoder if you wanted to output composite video or similar. You could even forego the DAC if you could live with basic digital colour.
Such a system would have a low resolution, limited by the CPU clock rate. To increase it you could use dual port RAM, with the CPU enabling the video side outputs and simply stepping through addresses as fast as possible. The outputs would create digital colour or feed an R2R DAC as above.
An improved version of this could use an address generating counter to step the RAM through addresses for each scanline. The CPU then only needs to set up the starting scanline address and trigger the counter to begin (and perhaps end). Using dedicated RAM would obviate the need for dual port RAM in that configuration. Adjusting the frequency of the counter also allows for different resolutions.