Cost efficient options for DAC using MSP430G2433

That's indeed the cheapest solution. However, the timer count and PWM resolution limits the upper frequency, and the filter limits the frequency range.
Some MSPs have internal DAC that gives better results. I used it to output a 50kHz sine wave (with 80 sample points per full wave), 12 bit resolution. On one of the later MSPs with up to 25MHz system clock, I could have done thee times as much. Of course, MSPs with DAC are more expensive than the G2433.
You can go for an external DAC. e.g. the DAC0808. You simply write the 8 bit output value to an MSP port and the DAC will output the corresponding analog value. Easy to interface. Fast (150ns settling time). And relatively cheap (<$1). Well, requires an 8-bit parallel connection, which on the small G2 devices takes most of the I/O lines. There are SPI -based DACs too

Several years ago there was an application report "Using PWM Timer_B as a DAC" SLAA116 - in the report, there are a couple different RC filters mentioned - you may want to consider the filter that uses 2 resistors and 2 capacitors ("two-pole stacked-RC filter).

Using the timer in OUTMOD_7 is quite precise - you can achieve good results with it. I've used this method to control the current in a cheapestcheap loop-powered transmitter. The good thing is that even if your timer clock isn't that stable/precise it doesn't really matter that much, because the variation affects the frequency and the dutycycle simultaneously. Of course an external DAC is the better solution, but produces extra costs.

But this depends on your requirements of the output signal.

Dennis