How much does DS2072A cost to make?
I would guess the majority of the cost is in three components: the two FPGAs, and the ADC.
The ADC is a 2GSa/s interleaved ADC (2ch x 1GSa/s) which could cost around $200 to $300.
The FPGAs probably cost $60 to $100 each.
The 800x480 LCD probably costs under $15.
Frontends are cheap. Rigol mostly use a passive front end with some active VGA/PGA circuit. Cost very low maybe $25 per channel. The trigger is a fast comparator or possibly just done on FPGA.
After that you've got a small-ish DSP probably ~$30 plus DDR2/3 (pretty cheap) and then stuff like the case, fan, power supply, misc electronics.
So I do expect Rigol have a good margin... but they also have a large R&D base, and they probably won't sell more than 1 million units in the product's lifespan... which means they have to account for this.