I'm not surprised.
In Europe, the common single phase power sockets are rated 230V, max. 16A, so the upper limit for a single phase input PSU is going to be about 3500 watts if the PSU has better than 95% efficiency. In the UK the limit's even lower, 240V 13A, so you wont find anything over 3000W.
*ANY* PSU that draws more than 13A (UK) or 16A (EU) from a single phase supply will be special purpose so won't be likely to be found in general distributor catalogs.