I'm definitely a flat-earther but be careful with arguments like these. The counter-argument would be that a bank surveillance camera costs 50 bucks while the system sending pictures back from "Mars" runs in the tens of millions of dollars.

No need to make many little arguments when the biggest and best argument is all you need: with the use of a strong telephoto lens, in countless places on earth, you can see landmarks and land masses that should be hidden beneath hundreds or even thousands of feet of curvature if the earth was really a sphere 25,000 miles in circumference. If every flat-earther beat this drum over and over again (and included their own examples and tests using lasers for instance) there would be no arguing it. But flat-earthers always let themselves get dragged into debates about unimportant things (i.e. "Why would the government lie to us?"). It's so very simple: where is the curve? If there's no curve, then there's no debate.