Depends on size. Brass/bronze or iron mould blocks will normally last longer and are well made. Outfits like NOE make excellent, extremely high quality aluminum moulds that make cheap aluminum moulds like Lee pale in comparison.
Lots of guys use nothing but Lee moulds - they are inexpensive compared to all others and work just fine for a lot of guys - I have 20 or more of them myself, - but- they are not as well made as ANY of the others I have, from: NOE, Tanner, Ohaus, RCBS, Saeco and Lyman.
Most of my 'standard' iron block moulds are Lyman. I have many single cavity, couple 4-cavity moulds and even a 6 cavity Lyman blocks. My Ohause are DC RB moulds, along with a couple RCBS DC moulds, round and conical. I have a set of Italian - Petroni or some-such name - mould blocks in .684" RB that are as good as any other of the iron blocks I have.
I now like to spray the interior and exterior of all my moulds, regardless of what they are made, with moly bullet spray. This coating assists in the moulds letting go of the ball as well as preventing any lead sticking to them. Rapine Mould Prep was another good mould coating. Soot from candle, match or propane lighter also works, but is not as permanent and needs removal and replenishing now and then.
Much also depends on what size or sizes you need as to what size is available from which maker. Tanner will make any size you want, for about $40.00 or 45.00 US. You will need Lyman or Lee handles for those.
Lee moulds cost from about $20.00 to $30.00 for single or DC & come with handles.
RCBS and Lyman moulds come without handles (buy separately) and run same as NOE moulds (no handles) - about - $90.00 to $150.00 or so, depending on size and # of cavities.