In 1957 they build the x15 if the Russians hadn't beat us in space we would have built the first space shuttle x20 in 1959 instead of 1963. In 1970 we started building the space shuttle, we did not replace it until 2007. And never built it. It took 2 years to go from space labs to the miir space station. We are still building a better space station. My point in these illustrations is that it takes longer to figure out better techs and stuff. Also how are you playing the game. When Iplay the game my research money I put into researching increases. Making the tech costs about the same throughout the game. Maybe your not playing the game right. Try using creativity on. Keep your approval at 70-75%. I think part of the problem is the slow population growth of the low approval everyone is talking about. You need at least some concentration

When you pay to rush build something the cost should gradually go down though.   The first time you build something it's a prototype so it's more expensive but when you start mass producing it, it should get cheaper.

For example the very first Ford T may have taken weeks to build, but once the assembly line was built to mass-produce it, one could come off it every 5 minutes or so.

The same can be said for technologies like VCR's.   At the very beginning in the early 1980's they cost close to 500$ to purchase.  The last VCR I bought cost me 28 $.