I don't know what brands you have available where you are, so I won't recommend any, but it is recommended you spend as much as you can on the receiver as it is the central hub of your system and dictates basically everything you are able to do with your setup. The differences between entry level and highend are pretty significant. As MistaEng stated build quality will differ greatly, highend receivers can weigh upwards of 60-70+ lbs which doesn't necessarily directly correlate to better quality but again as MistaEng said you get the point. Highend has better DAC's for better quality audio usually 192KHz 24bit, and more amplified channels for Dolby Digital EX and DTS ES (6.1), 7.1 and even 9.1 channel output. You also get more power per channel which should never be criteria you use to buy a receiver, as the difference between 140W and 100W is nill in the volume department. Highend has more connectors on the back so you can connect more components to your receiver. In addition to having more it has a better variety, multiple digital coax and optical for example, component video switching, LD AC-3 demodulater input (RF), 5.1 analog in, digital-in on the front panel, and so on and so forth. You will get a more versatile universal remote, often a touchscreen with the top of the line, and sometimes a second one if the receiver supports multiroom output. Higherend models often have on screen displays which allow you to setup your receiver on a TV screen as well as having far more options for you to control over your system. Often you will get more DSP modes and simulated surround sound modes which usually go unused and aren't really a selling point except to the newcomer. There are other differences, but those are the major universal ones. Different manufacturers will put their own little features on their topend models to differentiate them from the pack.
If you have certain features you are looking for, look for those first, then spend what you can over that. And as always, audition the equipment you want to buy before you buy it. There is no reason to spend huge money on something if one that costs half as much sounds just as good to you and has all the features you require.