Ethernet MTU is 1500 bytes (not 15000 bytes or 15 Kbyte), assuming non-jumbo frames. TCP MSS tends to be 1460 bytes. But then, opening a TCP connection requires

Ethernet MTU is 1500 bytes (not 15000 bytes or 15 Kbyte), assuming non-jumbo frames. TCP MSS tends to be 1460 bytes. But then, opening a TCP connection requires 3 packets anyway (so 4380 bytes.) TLS connections usually take another 2-3 packets (depending on your version of TLS/TLS parameters) so now your total payload just to establish the connection is sending 5840-7300 bytes over the wire. If we take the handshake as 50% overhead (which is quite sad mind you), then we can transmit a 7300 byte or 7.12 KB website, which can definitely make a pretty decent website. Optimizing for 1 kB can be a fun creative exercise, but I think it's practically a bit meaningless. It's better to target something like a 28.8 Kbps connection and try to get the page to load under a second (including connection handshake < 20.1 KB), which is more than enough to have a rich web experience.