I upgraded my service from 100A to 200A in 2009. Similar story to yours - it was an old, 100A, overstuffed panel. Whether or not your price is a good deal (or bad deal) depends on your area and other work involved, but I spent a similar amount and think the price seems reasonable.
I've been rewiring much of my home over the past few years, and I'm glad I jumped to 200A (which is what my Realtor recommended as well). Not because I needed 200A (I doubt I ever draw more than 100A), but because I've added at least half a dozen circuits since then to meet modern code requirements. So the extra space in the panel has been the biggest benefit. And the 200A is there if I need it.
I calculated my max electrical load based on the 2002 NEC code:
General Light and Receptacle Load 1536sqft x 3VA = 4608VA Small Appliance Circuits Load
2 x 1500VA = 3000VA Laundry Branch Circuit(s) Load
1 x 1500VA = 1500VA Total General Load Less Demand sum of above less T220.11 demand
sum of above = 9108VA
first 3000 at 100 % = 3000
next 117,000 at 35% = 2138
remainder at 25% = 0
sum less demand = 5138VA Fastened In Place Appliances Load
disposal = 720VA
dish washer = 912VA
fridge = 540VA
microwave = 1000VA
attic fan = 420VA
TV = 675VA
washing machine = 1200VA
sum less 75% demand = 4100VA Clothes Dryer Circuit(s)Load
Total dryer circuit(s) load = 5600VA Cooking Appliance(s) Load
T220.19 Column A = 0kVA
T220.19 Column B = 0kVA
T220.19 Column C = 0kVA
Total calc.d range load = 0kVA (gas range) Heating or Air-Conditioning Load
Air Conditioner = 4296VA Largest Motor Load
25% of largest motor = 0.25VA Total Computed Load 19134.25 Volt-Amps Computed Amperage
19134.25 divided by 240 = 80Amps
So I can potentially be at 80A right now. In the future i want to re-do my basement, which will add to the load, esp since I'd probably add electric baseboard.
Does code state that you cannot load your panel to 100% of capacity?